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UNIT – I (CRYSTAL PHYSICS)

PART – A QUESTIONS (2 MARKS)

1. Define unit cell.The unit cell is defined as the smallest geometric figure, the repetition of which gives the actualcrystal structure. (OR) A unit cell in !dimension is defined as that volume of the solid fromwhich the entire crystal can "e formed "y the translational repetition in !dimension.

#. $hat are %iller indices&%iller indices are the smallest possi"le integers which have the same ratios as the reciprocals ofthe intercepts of the plane concerned on the a'es.

. Define space (or) crystal lattice.A !dimensional collection of points in space is called space (or) crystal lattice.

. $hat is primitive cell& ive e'ample.A primitive cell is the simplest type of unit cell which contains one lattice points per unit cell.

*'ample+ imple cu"ic crystals.-. $hat is meant "y non!primitive cell& ive e'ample. on primitive cell is the unit cell as it contains more than one atoms or molecules in it. A non! primitive cell may "e dou"ly or /uadruply primitive cells.*'amples+ Dou"ly primitive cell !0ody centered cu"ic crystals. uadruply primitive cell !2ace centered cu"ic crystals.

3. $hat are 0ravais lattices& The 1 possi"le ways of arranging points in space lattice such that all the lattice points havee'actly the same surroundings. These 1 lattices are called the 0ravais lattices.

4. Define pac5ing factor (or) pac5ing density (or) density of pac5ing and give its unit.

6t is defined as the ratio of the volume of atoms per unit cell to the total volume occupied "y theunit cell.

A72 8

ince atomic pac5ing factor is the ratio it does not have any units.9. ame the seven crystal systems.

:u"ic Tetragonal Orthorhom"ic

%onoclinic Triclinic Rhom"ohedral ;e'agonal

<. Define co!ordination num"er.:oordination num"er in the no. of nearest neigh"oring atoms directly surrounding a given atom.

1=. Define atomic radius.



6t is defined as the half of the distance "etween two nearest neigh"ours in a crystal of pureelement.

11. :alculate the pac5ing factor of simple cu"ic (:) crystal structure.

7ac5ing factor 8

8

$e 5now, r 8 , therefore,

7ac5ing factor 8

A72 8 8 =.-#

1#. ame the crystal structure of the following+(a) old, (") ermanium, (c) 0arium and (d) >inc

old+ 2::ermanium+ Diamond cu"ic0arium+ 0::>inc+ ;:7

1. Define polymorphism and allotropy. (or) Differentiate polymorphism and allotropy. 7olymorphism+ A su"stance that can e'ist in two or more forms in the same state is called polymorphism. Allotropy+

An element that can e'ist in two or more forms in the same state is called allotropy1. Define 2ren5el and chott5y defect. (or) $hat are 2ren5el and chott5y

imperfections& 2ren5el defect is an ionic crystal imperfections that occurs when an ion moves into aninterstitial site, there"y creating two defects simultaneously i.e., one vacancy and the other self

interstitial. A pair of ion vacancies in an ionic crystal is termed as chott5y defect.1-. $hat is 0urger?s vector&

The vector which indicates the direction and magnitude of the shift of the lattice on theslip plane is called 0urger?s vector

13. ive the values num"er of atoms in unit cell of :, 0::, 2:: and ;:7. simple cu"ic(:) ! 1 atom



"ody centered cu"ic(0::) ! # atoms face centered cu"ic (2::) ! atoms ;e'agonal close pac5ed (;:7) ! 3 atoms

14. tate the coordination num"er for ;:7 and diamond structures. coordination num"er for ;:7 ! 1# coordination num"er for diamond structures !

19. $hat is meant "y closed pac5ed structure& ive one e'ample. The co!ordination num"er (1# and atomic pac5ing factor (=.4) are the same for "oth facecentered cu"ic and he'agonal closed pac5 structures, when we compare these structures withother structures, it has high pac5ing factor and hence it is called as closely pac5ed structure.*'amples+ %agnesium, >inc etc

1<. $rite the lattice parameters for triclinic crystal. 1. The three a'es are une/ual i.e., a@"@c. #. All three a'es are o"li/ue to each other i.e., @B@C@<=

#=. tate the e'pression for interplanar spacing for a cu"ic system interms oflattice constant and %iller indices.

The interplanar distance (d) 8

$here, a is lattice constant h, k, l are %iller indices#1.0ismuth has a8"8c8.4 AE and angles 8B8C83= what is its crystal structureiven a8"8c8.4 AE, 8B8C83= since the 8c8.4 AE and 8B8C83= it is a trigonal

##. tate the condition imposed on the cell parameters for crystal systems having the largest

num"er of "ravais lattices and the least num"er of nearest neigh"ours.1.crystal with least num"er of nearest neigh"ours is simple#. crystal with large num"er of "ravais lattice is orthorhom"ic The cell parameter for orthorhom"ic is a@"@c, 8B8C8<=

#. tate the values of num"er of atoms per unit cell ;:7 structure F D6A%ODnum"er of atoms per unit cell ;:783num"er of atoms per unit cell D6A%OD 89

#. $hich crystal structure is having least and large co ordination num"er&give e'ampleDiamond has the least co ordination num"er ie, ;:7 F2:: has the large co ordination num"er ie, 1#

#-. $hat are the lattice parameters of a unit cell&The lattice parameters of a unit cell are a,",c and ,B,C.



#3. $hat is principle used in 0ridgman techni/ue for growing crystals& 6n this techni/ue the material is heated to a very high temperature until the molten stage isreached.The molt is moved across the temperature gradient so as to solidify and form aseed.2urther such movements will lead to the crystal growth.

#4. $hat is the principle used cGochrals5i method&H:rystal pulling from the meltI is the principle used in cGocrals5i method. here the material ismelted over the monocrystalline seed and is roated.2urther with the help of a pull rod it is slowlydrawn upwards and hence the melt freeGes on the crystal and thus the crystal grows.

#9.;ow crystals are grown "y vapour phase& 6n this techni/ue the material to "e grown is supplied in the form of vapour.the powders of thedesired crystalline material are atomiGed "y e'posing it to an electric arc or hot flame.A seedcrystal is "rought some where near the melting point so that the arriving atoms or molecules will

have sufficiently high mo"ility on the growing surface.At very low temperature many crystals in a very high state of purity has "eengrown from thevapour phase.ynthetic ru"ies and sapphires are grown "y this method only

#<.$hat are the techni/ues adopted for growing crystals.The various crystal growth techni/ues are1.solution growth #.melt growth .vapour growth

=.what is meant "y solution growth&

The material to "e grown is dissolved using a solvent and is 5ept ideal until the super saturationstate is achieved.At some degree of supersaturation,parent nuclei is formed,which leads tofurther growth of crystal.The solvents commonly used are water ,organic li/uids (or) molten salts.

1.Jist out the various types of melt growth.The various melt group techni/ues are1.ormal freeGing#.:rystal pulling.>one melting.2lame fusion

#. $hat is "asis (or) %otif&A unit assem"ly of atoms or molecules(ie,one or more atoms (or)molecules)identical incomposition,arrangement and orientation is called the "asis (or) %otif. A crystal structure is formed "y associating a "asis to every lattice 7oint in a space lattice.



. $hat is a crystal structure&A crystal structure is formed "y associating a "asis to every lattice point in a space lattice.6e, crystal structure 8 0asis K space lattice

. Define interatomic distance and interplanar distance&

6nteratomic distance + The distance "etween any # atoms is called interatomic distance .6nterplanar distance + The distance "etween any # plane are called interplanar distance.

-. ive the relation "etween density of the crystal and the lattice constant.The relation is

L8

where n is the num"er of atoms per unit cell, is the adro num"er, L is the atomic weight and a isthe lattice constant.

3. $hat is an amorphous solid&ive e'ample.6t is a type of solid,in which the atoms or molecules are not arranged in an orderly fashion. 6e.,the same atomic groups are arranged more randomly.*'ample+7lastic,ru""er.

PART – B QUESTIONS (16 MARKS)

1. Determine co!ordination num"er, atomic radius and pac5ing factor for ahe'agonal close pac5ed (;:7) structure. how that an ;:7 structure demands an a'ialratio of 1.33.plit of %ar5s M Answer 5ey+:o!ordination num"er N %ar5sAtomic radius N %ar5s7ac5ing factor N %ar5s;:7 structure demands an a'ial ratioN %ar5s

#. (i) $hat are %iller indices&(ii) Derive an e'pression for the interplanar spacing for (h k l ) planes of a

cu"ic structure.plit of %ar5s M Answer 5ey+%iller indices N# %ar5s*'pression for the interplanar spacing N1 %ar5s

. (i) how that the face centered cu"ic and he'agonal close pac5ed structure hasthe same atomic pac5ing factor. (ii) how that for a cu"ic structure the interplanar distanced? in terms of

%iller indices and the cell edgea? is given "y (d) 8

plit of %ar5s M Answer 5ey+:entered cu"ic and he'agonal close pac5ed structure N9 %ar5s



%iller indices and the cell edge N9 %ar5s. (i) Define pac5ing factor.

(ii) Deduce the cMa ratio and pac5ing factor for ;:7 structure.plit of %ar5s M Answer 5ey+7ac5ing factor N# %ar5s

cMa ratio and pac5ing factor for ;:7 structure N1 %ar5s-. (i) $hat are 0ravais lattice& Descri"e using diagrams of unit cell the

different 0ravais lattices and their grouping into the seven crystal system.(ii) Descri"e the arrangement of atoms in 2:: and ;:7 structure and show

that "oth these structures have the same atomic pac5ing factor.plit of %ar5s M Answer 5ey+0ravais lattice N# %ar5s0ravais lattices and their grouping into the seven crystal system N3 %ar5sAtoms in 2:: and ;:7 structure and atomic pac5ing factor N9 %ar5s

3. (i) *'plain diamond cu"e structure and o"tain its atomic pac5ing factor. Also

descri"e the arrangement of atoms in >n.(ii) $hat are line defects& *'plain edge dislocation using a diagram.plit of %ar5s M Answer 5ey+Diamond cu"e structure N#%ar5s7ac5ing factor N# %ar5sArrangement of atoms in >n N%ar5sJine defects N %ar5s*dge dislocation using a diagram N- %ar5s

4. Define co!ordination num"erFum"er of atoms per unit cell. calculate theco!ordination num"er Fum"er of atoms per unit cell for simple cu"ic, "ody centredcu"ic and face centre cu"ic structures.Definition for :o!ordination num"er F num"er of atoms per unit cell N %ar5sco!ordination num"er Fum"er of atoms per unit cell forsimple cu"ic structures. N %ar5s

:ordination num"er Fum"er of atoms per unit cell for "ody centred cu"ic structures. N %ar5s

:ordination num"er Fum"er of atoms per unit cell for2ace centred cu"ic structures. N %ar5s

9.Define atomic radius F 7ac5ing factor for simple cu"ic, "ody centred cu"ic and face centrecu"ic structures.Definition for Atomic radius F pac5ing factor !mar5sAtomic radius F pac5ing factor forsimple cu"ic structures. !mar5sAtomic radius F pac5ing factor for



0ody centred cu"ic structures. !mar5sAtomic radius F pac5ing factor for2ace centred cu"ic structures. !mar5s

<.ive the procedure for finding miller indices of crystal plane

%iller indices N# %ar5s*'pression for the interplanar spacing N1 %ar5s

1=.how that an ideal he'agonal closed pac5ed structure cMa81.3 F density of atomic pac5ing factor e/ual to that of 2::P7ac5ing factor N# %ar5scMa ratio and pac5ing factor for ;:7 structure N1# %ar5s;:782:: !#%ar5s.

11. Define atomic pac5ing factor,calculate the pac5ing factor fori) : ii) 0:: iii) 2:: iv) ;:7 v) Diamond unit cells.

: ! %ar5s0:: ! %ar5s2:: ! %ar5s;:7 ! %ar5sDiamond ! %ar5s

1#.*'plain the 0ridgman and cGochrals5i techni/ues for growing crystals.0ridgman techni/ues+ 7rinciple !#%ar5s

:onstruction !%ar5swor5ing !%ar5sAdvantages !1%ar5sDisadvantages !1%ar5s

cGochrals5i techni/ues + 7rinciple !#%ar5s

:onstruction F wor5ing !%ar5sAdvantages F Disadvantages !1%ar5s

1.Descri"e the various crystal growth and techni/ue

various crystal growth and techni/ues !#%ar5ssolution growth !#%ar5smelt growth !#%ar5svapour growth !#%ar5s0ridgman techni/ues! ar5scGochrals5i techni/ues !%ar5s



UNIT II

PROPERTIES OF MATTER AND THERMAL PHYSICS


1. *'plain neutral a'is.The middle layer (or) filament of a "eam which remains unaltered even with the presenceof load on the "eam is called neutral a'is. 2ilaments which are lying a"ove it areelongated and those are lying "elow it are compressed.

#. $hat are the effects of hammering and annealing on elasticity of a material&$hile "eing hammered (or) rolled, crystal grains "rea5 into smaller units resulting inincrease of their elastic properties. $hile annealing (that is, heating and then coolinggradually) constituent crystals are uniformly oriented and form larger crstal grains,whichresults in decrease in their elastic properties.

. %ention the factors affecting the elasticity of a material.

Temperature

6mpurities ;ammering, rolling and annealing

stress. *'plain "ending moment of the "eam.

The moment of the couple due to the elastic reactions (restoring couple) which "alancesthe

e'ternal couple due to the applied load is called the "ending moment.-. Define stress and strain and write down their units.

tress+ tress is defined as the restoring force per unit area which "rings "ac5 the "ody toits original state from the deformed state. Enit is Mm# .train+ strain is defined as the change in dimension produced "y the e'ternal force on the "ody. 6t can also "e defined as the ratio of the change in dimension to the originaldimension. 6t has no unit.

train 8





The ma'imum stress upto which a "ody can recover its original shape and siGe, afterremoving the e'ternal forces is called as elastic limit.After elastic limit, if the elasticity of the "ody is completely lost, then the "ody will "e ina limit called as plastic limit.

1. Define yield point.

6f the e'ternal stress applied is very large, then the "ody will lose its elastic property,even after the removal of the stress.The point at which the "ody loses its elasticity (elastic nature) is called as yield point.

1-. Define plastic fatigue.6f a "ody is continuously su"Sected to stress (or) strain, it gets fatigued (wea5) called aselastic fatigue.

13. $hat are the factors affecting elasticity.

*ffect of stress

*ffect of annealing

*ffect of temperature 7resence of impurities

*ffect due to the nature of crystals.14. $hat is meant "y annealing&

Annealing is a process "y which the material is heated to a very high temperature andthen it is slowly cooled. Esually this process is adopted for a material to increase thesoftness and ductility of the materials. Annealing also reduces the elastic property of thematerial, due to the formation of large crystal grains in it.

19. Define young?s modulus.6t is defined as the ratio "etween the longitudinal stress to the longitudinal strain, withinthe elastic limit.

8 8 (m!#)

1<. Define "ul5 modulus.0ul5 modulus is defined as ratio "etween the volume stress to volume strain withinelastic limit

8 8 (m!#)

#=. Define rigidity modulus.6t is defined as the ratio "etween the tangential stress to the shearing strain, within theelastic limit.



n 8 8 (m!#)

#1. what is poisson?s ratio&

6t is defined as the ratio "etween the lateral strain per unit stress (B) to the longitudinalstrain per unit stress() within the elastic limit poisson?s ratio(U)8 lateral strain 8 B 8 a constant longitudinal strain

##. ive the relation "etween modulii. 8 <5n 5Kn$here

8young?s modulus

V8"ul5 modulus

n8rigidity modulus

#. what is moment of force&

The moment of a force s"out a point is defined as the product of the magnitude of the force ofthe particular distance from the point to the line of action of force

#. define tor/ue.

Tor/ue is a rotating force and is e/ual to the moment of the couple.Tor/ue is the product of oneof the force from couple and the perpendicular distance "etween # opposite forces.

#-. Define "eam.

A "eam is defined as rod or "ar of uniform cross section whose length is verymuch greater thanits other dimensions such as "readth F thic5ness.

#3. Define cantilever.

A cantilever is a "eam fi'ed horiGontally at one end F loaded at other end

#4. Define 6!shape girder.

The girder is the one in which the upper and lower section are "roadened and middle of thesection is tapered so that it can withstand heavy load over it.since the girder loo5s li5e letter 6 , itis called as 6!shape girder.

#9. ive the applications of 6!shape girder.



They are used in construction of the "ridge over the river.

They are verymuch useful in the production of iron rails which are employed inrailway trac5s.

They are used as supporting "eam for the ceiling in the construction of "uildings.#<. $hat are the "asic entities responsi"le for thermal conduction of solid&

Area of the cross section (A)

Temperature difference "etween hot and cold layers.

Time of the conduction (t)

Thic5ness of the solid (').

=. Define co efficient of thermal conductivity&

6t is defined as the amount of heat conducted per second normally across the unit area of crosssection maintained at unit temperature gradient.

V 8 $m!1V !1

1. ;ow are heat conduction and electrical conduction analog as to each other&

;*AT :ODE:T6O+

6t is conducted from high temperature point to low temperature point

6n metals it is mainly due to free electrons and the contri"ution due to latticevi"ration is negligi"le.

6n non metal heat conduction is due to lattice vi"ration

*J*:TR6:AJ :ODE:T6O+

6t is conducted from high potential point to low potential point.

6n metal it is due to electrons.

6n semiconductor "oth electrons and holes contri"ute for the electricalconduction.6n insulator at high voltage electric "rea5down occurs.



#. what is :onduction&

6t is the process in which the heat is transferred from hot end to cold end without movement of

particles.. what is :onvection&

6t is the process in which the heat is transferred from hot end to cold end with movement of particles

. what is radiation&

6t is the process in which the heat is transferred from one phase to another phase without thenecessity of the intervening medium.(sum reacting earth).

-. $hat is meant "y temperature gradient&

The rate of fall of temperature with respect to the distance is called temperature gradient.6t isdenoted as N(dWM d').

The negative sign indicate the fall of temperature with increase in distance.

3. Define thermal diffusivity&

6t is defined as the ratio of thermal conductivity to the thermal capacity per unit volume ofmaterial.

Thermal diffusivity8 thermal conductivity Mthermal capacity

6t is the product of specific heat capacity and density of material

; 8 m#s!1

4. Define newton?s law of cooling.

The rate of loss of heat of "ody is directly proportional to the temperature difference "etween the "ody and its surrounding,of same nature.

9. Derive the unit for thermal conductivity.

The thermal conductivity of material is



V 8

8 8

The unit of the thermal conductivity is $m!1V !1

<. ive the methods of determining the thermal conductivity of good and "ad conductors.

The methods used for determining the thermal conductivity of good and "ad conductors are+

earle?s method N good conductor

2or"e?s method N for determing a"solute conductivity of metals

Jee?s disc method N for "ad conductors

Radial flow method N for "ad conductors.

=. what is the principle employed in searle?s method&

Amount of heat conducted "etween the two points in a rod per second is calculated.This heat iso"served "y the water flowing through the tu"es per second under steady state conduction,theamount of heat flowing through any section of the rod per seconds is e/ual to the amount of heat

gained "y the water per second.

;eat conducted "y the section of the rod8 ;eat gained "y the water 1. why the specimen used to determine thermal conductivity of a "ad conductor should have

a larger area and smaller thic5ness&

2or a "ad conductor with a smaller thic5ness and larger area of cross section,the amount of heatconducted will "e more.

#. what is meant "y thermal resistance&

The thermal resistance of a "ody is a measure of its opposition to the flow of heat through it. (ie)every"ody posses some resistive power when it is su"Sected to heat. This resistive power istermed as thermal resistance.


1. Derive a differential e/uation to descri"e the heat conduction along a uniform "ar. ;enceo"tain the steady state solution of it.



Rectilinear flow of heat ! %ar5s

0efore steady state is reached ! %ar5s

after steady state is reached infinite length ! %ar5s

after steady state is reached finite length ! %ar5s

#. O"tain an e'pression for the /uantity of heat conducted radially out of a hollow cylinder.Esing this, e'plain how the thermal conductivity of ru""er can "e determined.

Radial flow of heat ! #%ar5s;ollow cylinder ! %ar5sThermal conductivity of ru""er !1= %ar5s

. Derive the e/uation for heat conduction along a "ar and solve it for steady statecondition.

Rectilinear flow of heat ! %ar5s

0efore steady state is reached ! %ar5s

after steady state is reached infinite length ! %ar5s

after steady state is reached finite length ! %ar5s

. Discuss with necessary theory the method of determining the thermal conductivity in the

form of a tu"e.

Description ! %ar5s

$or5ing ! 4%ar5s

Ender steady state ! 3%ar5s

-. Derive an e'pression for thermal conductivity of the material of a thic5 pipe throughwhich a hot li/uid is flowing.

7rinciple ! #%ar5s

:onstruction! %ar5s

wor5ing! -%ar5s



derivation! -%ar5s

3. Derive the e/uation for one dimensional flow heat and solve it under steady statecondition.

Rectilinear flow of heat !%ar5s

0efore steady state is reached

i)7art of the heat is used to raise the temperature of the rod !#%ar5s

ii)Rest of the heat is radiated from the surface of the rod !#%ar5s

after steady state is reached infinite length !%ar5s

after steady state is reached finite length(l)(covered with insulating materials) !%ar5s

4. Derive an e'pression for the /uantity of heat flow through a metal sla" whose faces are5ept at two different temperatures. Ese this e'pression to determine the thermalconductivity of a "ad conductor "y Jee?s disc method.

7rinciple !# %ar5s

Description !# %ar5s

wor5ing! %ar5s

:alculation! %ar5s

Rate of cooling !3 %ar5s

9. Derive an e'pression for the radial flow of heat through a cylindrical tu"e.

Radial flow of heat ! #%ar5s;ollow cylinder ! %ar5sThermal conductivity of ru""erDescription !# %ar5s

$or5ing ! %ar5s



:alculation ! %ar5s

<. Descri"e with necessary theory, the method to determine the young?s modulus of the

material of a rectangular "ar "y uniform "ending.Theory !9%ar5s

tatistical method !%ar5s

raphical(or) dynamical method ! %ar5s

1=. $hat is cantilever& O"tain an e'pression for the depression at the loaded end of acantilever whose other end is fi'ed assuming that its own weight is not effective in "ending.

:antilever+ A cantilever is a "eam fi'ed horiGontally at one end and loaded at theother end ! # %ar5s

Depression theory N 1= %ar5s

pecial cases+ (i) Rectangular cross section N # %ar5s

(ii) :ircular cross section N #%ar5s

11. Descri"e an e'periment to determine the young?s modulus of a "eam using "ending of "eams.

7rinciple !# %ar5s

Theory !# %ar5s

*'pression! %ar5s

tatistical method! %ar5s

raphical method! %ar5s

1#. Derive an e'pression for the internal "ending moment of a "eam in terms of radius of

curvature.

7rinciple !# %ar5s

Theory !# %ar5s

*'pression! %ar5s



tatistical method! %ar5s

raphical method! %ar5s

1. A circular and a s/uare cantilever are made of same material and have e/ual area of cross

N section and length. 2ind the ratio of their depressions for a given load.:antilever+ A cantilever is a "eam fi'ed horiGontally at one end and loaded at the otherend ! # %ar5s

Depression theory N 1= %ar5s

pecial cases+ (i) Rectangular cross section N # %ar5s

(ii) :ircular cross section N #%ar5s

1. (i) :lassify different types of elastic modulus and e'plain it.

(ii) $rite a short note on 6 N shaped girders.

(i) Types of elastic modulus+

oungs modulus, 0ul5 modulus, Rigidity modulus N # %ar5s

*'planation N 3 %ar5s

(ii) 6!shaped girders

Definition N # %ar5s

*'planation N %ar5s

Application!# %ar5s

1-. (i)$rite a short notes on stress strain diagram.

(ii)*'plain the factors affecting the elasticity.

tress strain diagram *'planation!9 %ar5s

2actors affecting the elasticity!9 %ar5s

13. (i);ow will you classify three types of elastic modulii& *'plain.

(ii)Define ;oo5e?s Jaw, 7oisson?s ratio, *lastic limit and ield point.

Types of elastic modulus+

oungs modulus, 0ul5 modulus, Rigidity modulus N # %ar5s



*'planation N 3 %ar5s;oo5e?s Jaw, !# %ar5s

7oisson?s ratio, !# %ar5s

*lastic limit and !# %ar5sield point!# %ar5s

14. (i) Derive the relation "etween three modulii.

(ii) $rite a short note on 6 N shaped girders

(i) The relation "etween three modulii! %ar5s

(ii) 6!shaped girders

Definition N %ar5s*'planation N - %ar5s

Application! %ar5s

19. $hat is meant "y radial flow method. Descri"e any one of the method to find the thermalconductivity of a "ad conductor.

Radial flow of heat ! #%ar5s;ollow cylinder ! %ar5s

Thermal conductivity of ru""erDescription !# %ar5s

$or5ing ! %ar5s

:alculation ! %ar5s

1<. ;ow will you determine the thermal conductivity of a poor conductor e'perimentally&

7rinciple !# %ar5s

Description !# %ar5s

wor5ing! %ar5s

:alculation! %ar5s

Rate of cooling!3 %ar5s



UNIT III QUANTUM PHYSICS


1. *'plain 7lanc5?s hypothesis (or) what are the postulates of 7lanc5?s /uantum theory&

(%ay #==) The "lac5 "ody radiation cham"er is filled up not only with radiations "ut alsowith large num"er of oscillating particles. The particles can vi"rate in all possi"le fre/uencies.

The fre/uency of radiations emitted "y an oscillator is the same as that of thefre/uency of the vi"rating particles.

The oscillatory particles cannot emit energy continuously. They will radiateenergy only in the form of a discrete pac5et of energy, i.e., a small unit called/uantum or photon.

The vi"rating particles can radiate energy when the oscillators move from one

state to another. The radiation of energy is not continuous, "ut discrete innature. The values of the energy of the oscillators are li5e =, h ϒ,#h ϒ, h ϒ,

X..n h ϒ.

#. $hat is meant "y "lac5 "ody and "lac5 "ody radiation& (%ay #==)A perfect "lac5 "ody is one which a"sor"s radiation of all wavelengths incident on it.

2urther, such a "ody cannot transmit or reflect any radiation and therefore it appears "lac5. A "lac5 "ody can radiate energy in all possi"le wavelengths when it is heated to a suita"letemperature. The radiation emitted from "lac5 "ody is 5nown as "lac5 "ody radiation or totalradiation.

. tate :ompton *ffect. (or) ive a "rief account on :ompton *ffect. (Yune #==3, %ay#==4)

$hen a monochromatic "eam of !rays having wavelength λ? is allowed to fall on a "lac5of paraffin or car"on, the "eam is scattered into two components. One of the components has awavelength e/ual to the incident wavelength and the other has a higher wavelength compared tothe incident wavelength. This phenomenon in which there is change in wavelength of thescattered !rays is called :ompton shift and the effect is 5nown as :ompton *ffect.

. $hat is :ompton wavelength& ive its value. (April #==, Yan #==<, Yan #=1=) 6 :ompton e'periment, scattered "eam consists of !rays of two components, one with a

wavelength e/ual to the incident wavelength and the other has a higher wavelength compared to

the incident wavelength. The :ompton shift or :ompton wavelength dλ8λ?!λ8 (1!cosφ).

$hen the scattering angle φ8=Z, dλ8=

$hen the scattering angle φ8<=Z, dλ8 8 =.=##4 [



$hen the scattering angle φ8 19=Z, dλ8 8 =.=9-[

-. $hat is the physical signification of a wave function& (Dec #==#, ov #==, %ay #==,Yan #==3, %ay #==9, Yan #==<, Yan #=1=)

o 6ts relates the particles and wave nature of mater elastically.o 6t provides the information a"out the particle "ehavior.

o 6t is the comple' /uantity and hence we cannot measure it.

o The s/uare of the wave function is a measure of the pro"a"ility of finding the particle at a particular position. 6t cannot predict the e'act location of the particle.

o The wave function is a comple' /uantity, where as the pro"a"ility is a real and positive /uantity. Therefore, position pro"a"ility density 7(r,t) is defined as the product of the wave function and its conSugate as,

7(r.t)8\ (r,t)\Q (r,t)8]\(r,t) ]#

o The pro"a"ility of finding the particle within a volume of dτ is 78 dτ, where dτ8 d'dydG.

o 6f the particle is definitely present, then its pro"a"ility value is one.

i.e., 78 dτ 8 1.

o 6f the pro"a"ility density (7) 8= then the chance to find the partied within thevolume is Gero.

o The wave function has no physical meaning, where as the pro"a"ility density has

a definite physical meaning.3. $hat is meant "y photon& ive its properties. (Yan #==9)The discrete energy values in the form of small pac5ets or /uantas of definite fre/uency

or wavelength are called photons. 7hotons propagate li5e a particle with speed of light as 1=9

ms!1

7ropertieso 7hotons will not have any charge. They are neutral and hence they are not

affected "y magnetic and electric field.o They do not ioniGe gases

o The energy of one photons is given "y *8h ϒ, which varies with respect tothe type of radiation fre/uencies.

o %ass of the photons is given "y m8 and momentum of the photon is

given "y 78hMλ

4. $hat is the wave function&



A varia"le /uantity which characteriGes de!0roglie waves is 5nown as wave function and isdenoted "y the sym"ol \. The value of the wave function associated with a moving particle at point (',y,G) and time t? gives the pro"a"ility of finding the particle at that time and at that point.9. $hat is chrodinger wave e/uation&chrodinger wave e/uation is a mathematical e/uation descri"es the dual nature of matter waves.chrodinger e/uation is one of the "asic /uantum mechanical e/uations. This e/uation is used todescri"e "oth macroscopic as well as microscopic particles.<. tate the principle of *lectron microscope. (Yan #==<)

A stream of electrons can "e focused "y a suita"le electric and magnetic fields and passedthrough the o"Sect. These electrons carry the information a"out the o"Sect.1=. $hat is meant "y degenerate and non! degenerate state& ive e'amples.1. Degeneracy

Different wave functions with three different /uantum num"ers may "e have same energyvalue. $e have same energy *igen value "ut different *igen functions. uch states and energy

levels are called degenerate state.*'amples+ The different states having uantum num"ers (1,1,#), (1,#,1), and (#,1,1) have thesame energy.#. on!degeneracy

6f only one *igen function corresponding to certain energy, the state and the energy levelare said to "e non!degenerate state.

*'amples+ The /uantum num"ers (1,1,1) has the energy no other state has this energy.

11. Differentiate "etween optical microscope and electron microscope.

.o Optical microscope *lectron microscope1. ;ere, the source is an incandescent

lamp.;ere, the source is an electron gun.

#. 6ts principle is "ased on a"sorption oflight.

6ts principle is "ased on transmission ordiffraction of electrons.

. 6t is made up of lens systems. 6t is made up of electromagnetic lens.. o need of vacuum. ;igh vacuum is needed.-. Resolving power is =.====# cm. Resolving power is 1[.3. Resolution is poor. Resolution is good.4. %agnification is #=== times as that of

the siGe of the o"Sect.%agnification is more than 1=- times as that ofthe siGe of the o"Sect.

9. 6t is low cost. :ost is high.<. :ompact in siGe. iGe is larger.

1#. :ompare *% and T*%. (Yan #==<).o. canning *lectron %icroscope Transmission *lectron %icroscope

1. econdary electrons mainly used forimage formation.

The transmitted or diffracted electrons aremainly used for image formation.

#. %agnification is , ==,=== times %agnification is 1=3 times greater than that of



greater than that of the siGe of theo"Sect.

the siGe of the o"Sect.

. The resolution is a"out 1= to #= nm. The resolution is a"out =.# nm.. 6t gives !dimensional image. 6t gives #!dimensional image.-. ample preparation is comparatively

easy.

ample preparation is difficult.

3. 6t is used for the specimen with largerthic5ness.

6t is not suita"le for thic5 sample.

4. 6t is suita"le for "iological samples. 6t is not suita"le for "iological samples.1. Distinguish "etween T*% and T*%. ((Yan #=1=).o. T*% T*%

1. 6t provides a two dimensional imageof the samples.

6t provides a three dimensional image of thesamples.

#. %agnification is 1=3 times. %agnification is more than 1=3 times.. The resolution is a"out =.# nm. The resolution is a"out =.1 nm.. 6t is not suita"le for "iological

samples.

6t is suita"le for all 5inds of samples including

"iological samples.

1. $hat is the principle of T*%& (OR) *'plain the principle of transmission electronmicroscope. (%ay #==9, Yune #==<)

$hen the high energy accelerated electrons are focused on a sample, they can passthrough the sample and image is formed in the screen either "y transmitted "eam or diffracted "eams. This gives the three dimensional image of the sample.1-. ive the special features of /uantum theory of radiation. (Yan #==<)

1. $e can deduce tefan N 0oltGmann?s law, $ien?s displacement law and Rayleigh NYean?s law from /uantum theory of radiation.

#. $ien?s displacement law holds good only for shorter wavelength and Rayleigh NYean?s law holds good for longer wavelength. 0ut 7lanc5?s /uantum theory of radiation holdsgood for longer and shorter wavelengths.

. According to /uantum theory of radiation, we 5now that the e'change of energy values "etween the light radiation and particles have discrete energy values 5nown as photons.13. $rite down the chrodinger time independent and dependent wave e/uations. (Apr1<<)

(i) chrodinger time independent e/uation,

∇#\K (*!^) \ 8=

(ii) chrodinger time dependent e/uation,;\8*\$here,∇ is the Japlacian operator



* is the energy operator ; is the ;amiltonian operator.

14. Define $ien?s displacement law and write its limitation. ((Yan #=1=)According to $ien?s displacement law in the energy spectrum of a "lac5 "ody, the

product of the wavelength corresponding to ma'imum energy and a"solute temperature is aconstant.

λm T 8 constant

Jimitation+ 6t is applica"le for short wavelength only.19. tate Rayleigh N Yean?s law. $hat are its limitations& ((Yan #=1=)

According to Rayleigh N Yean?s law, the energy distri"ution in the "loc5 "ody spectrum isgiven "y.

*89_5 0TMλ

$here, 5 is 0oltGmann constant. The energy distri"ution is directly proportional to the a"solutetemperature and is inversely proportional to the fourth power of the wavelength.

Jimitation+ 6t is applica"le for longer wavelength only.1<. $rite the principle of T*%. (%ay #==9) $hen the high energy accelerated electrons are focused on a sample, they can passthrough the sample and image is formed in the screen either "y transmitted "eam of diffracted "eam. 6t gives the three!dimensional image of the sample.

#=. $hat is "lac5 "ody and what are its characteristics& (%ay #==9)A perfect "lac5 "ody is the one which a"sor"s radiation of all wavelength incident on it

and also emit all wavelength of radiation.:haracteristics 1. 7ractically, there is no perfect "lac5 "ody #. $e can artificially paint the "lac5 colour over the surface to ma5e "lac5 "ody . 6t is a perfect a"sor"er and radiator . Radiation emitted from "lac5 "ody is 5nown as "lac5 "ody radiation.#1. $rite an e'pression for the wavelength of matter waves.(or) $hat is de!0roglie wavee/uation& (%ay #==3)

de!0roglie wavelength (λ)8 8

where, h!is the 7lanc5?s constant. m!is the mass of the particle. v!is the velocity of the particle. p!is the momentum of the particle.##. tate the properties of the matter waves. (ov #==#)



1. The wavelength associated with matter wave get shorter when the mass of the particles "ecomes larger.

#. %atter waves are electromagnetic waves.. The function of matter wave is to guide the matter particles` hence it is called as pilot

wave.

. These waves can travel faster than the velocity of light-. The velocity of matter wave is not a constant.3. The phase velocity of matter wave is inversely proportional to its wavelength.

#. *'plain the signification of de!0roglie e/uation& (April 1<<4)1. de!0roglie e/uation connects the particle and its associated waves.

#. 6t gives the matter wave wavelength λ 8

#. An electron at rest is accelerated through a potential of -===^. :alculate the de!0rogliewavelength of matter wave associated with it. (April #==)

λ8hM( )

λ83.3#- 1=!M( # <.1 1=!1 1.3=# 1= !1< -==

λ8=.14- 1= !1=

#-. 2ind the change in wavelength of an !ray photon when it is scattered through an angle of1-Z "y a free electron. (%ay #==4)

83.3#- 1=!M(<.1 1=!1 1= 9)(1!cos1-Z)

8 =.=13 1=!1= m

#3. :alculate the de!0roglie wavelength of an electron which can "een accelerated through a potential of ==^

λ8hM( )

λ83.3#- 1=!M( # <.1 1=!1 1.3=# 1= !1< ==

λ8=.31- 1= !1=m



#4. The wavelength of ' ray photon is dou"led when it is scattered through an angle of <=Z "y atarget material.find the incident wavelength.2ormula+

#λ?!λ8

8 )

λ83.3#- 1=!M(<.1 1=!1 1= 9(1!cos<=Z)

λ8=.=## 1=!1= m

#9. 6n :ompton scattering, the incident photon have wavelength of 1=!1=m. :alculate the

wavelength of scattered radiation if they are viewed at an angle of 3=Z to the direction ofincidence. (Yan #=1=)

8.=1#1 1=!1= m

#<. :alculate the */uivalent wavelength of electron moving with a velocity of 1=4ms!1 .

(Yan #=1=)=. tate 5irchoff?s law of radiation& The ratio of emissive power to the coefficient of a"sorption of any given wavelength is samefor all "odies at given temperature and is e/ual to the emmisive power of the "lac5"ody at thattemperature.

6e., eλMaλ 8 *1.2or a free particle moving within a one dimensional potential "o',the groundstate energy cannot "e Gero,why&2or a free particle moving within a one dimensional potential "o',when n8= thewave function is Gero for all values of '.it is Gero even within the potential "o' this





.the magnification upto ===== time greater than the o"SectD6ADÂTA*+1.The resolution of the image is 1= to #= nm

4. %ention the application of *%.

1.6 t is used to e'amine the structure of specimen in !d view#. 6s microscope has also has wide range of applications li5e "iology,industrial,engineering etc

9. Jistout the advantages and disadvantages of T*%.ADÂTA*+1.6t can "e used to e'amine the specimen of siGe upto =.# nm#.T magnification is 1====== time greater than the siGe of o"Sect.6t has high resolution.The resolving power is 1 [ to #[

D6ADÂTA*+1.The specimen should "e very thin#.6t is not suita"le for thic5 sample.There are chances for the structural change, during sample preparation..The !D image cannot "e o"tained

<.%ention the application of electron microscope.1.6t has a very wide area of applications in the field of "iology, metallurgy, physics, chemistry,medicine and engineering.#.6t is used to determine the complicated structures of crystals.

.6t is used in the study of celluloids..6t is used t study the structure of micro organisms such as virus, "acteria etc.

=.Define ormalisation process and write down the normaliGed wave function for an electronin a one dimensional potential well of length a? metres. ormalisation is the process "y which the pro"a"ility of finding a particle inside any potentialwell can "e done. 2or a one dimensional potential well of length?a? metre the normaliGed wave function is given "y

\n


1. (i).$rite a note on "lac5 "ody radiation. (ii).Derive 7lanc5?s law of radiation (Yan #=1=)



plit of %ar5s M Answer 5ey+0lac5 "ody radiation N 3%ar5s7lanc5?s law of radiation N 1=%ar5s#. Derive chrodinger time dependent and time independent e/uation.(Yan #==<)plit of %ar5s M Answer 5ey+chrodinger time dependent e/uation N 1=%ar5schrodinger time independent e/uation N 3%ar5s

.(i).$hat is :ompton effect& (ii).ive the theory of :ompton *ffect and show that the :ompton shifts

dλ8 (1!cosφ) (Yan #==-)

plit of %ar5s M Answer 5ey+:ompton *ffect N #%ar5s

Theory of :ompton *ffect N %ar5s:ompton shift dλ8 (1!cosφ) N 1=%ar5s

. (i).*'plain 7lanc5?s hypothesis. (ii).tate and derive 7lanc5?s law of radiation. (Yan #==<)plit of %ar5s M Answer 5ey+7lanc5?s hypothesis N %ar5s7lanc5?s law of radiation N 1#%ar5s-. *'plain the application of chrodinger wave e/uation to a one dimensional potential

well. Outline the characteristics of the wave function. (Dec #==, %ay #==9)plit of %ar5s M Answer 5ey+Application of chrodinger wave e/uation to a one dimensional potential N 1#%ar5s:haracteristics of the wave function N %ar5s3. Derive energy for energy distri"ution "ased on the concept of /uantum theory of "lac5 "ody radiation. 2rom that, derive $ien?s displacement law and Rayleigh!Yeans law. (Yan#==<)plit of %ar5s M Answer 5ey+Theory of "lac5 "ody radiation N 1= %ar5s$ien?s displacement law N %ar5sRayleigh!Yeans law N %ar5s4. (i).Derive chrodinger?s time independent wave e/uation for a particle trapped in a onedimensional potential well of infinite depth and o"tain the eigen value and eigen function. (ii).*'plain with a neat diagram the wor5ing of scanning electron microscope.plit of %ar5s M Answer 5ey+Diagram F *'planation N # %ar5s





7rinciple N # %ar5s

UNIT – IV ULTRASONICS


1. ame the methods "y which ultrasonic waves are produced. (%ay #==) %echanical generators and electrical generators. %echanical generators areclassified into gas driven and li/uid driven. *lectrical generators are classified intomagnetostriction generator and pieGo!electric generator.#. Are the ultrasonic waves are electromagnetic waves& ive proper reasons to youranswer. (Yan 1<<4)

o. Eltrasonic waves are not electromagnetic waves. Eltrasonic waves are highfre/uency sound waves. There is no electric and magnetic vectors in Eltrasonic waves as inelectromagnetic waves.

. %ention the properties of Eltrasonic waves. (Yan 1<<9, Dec. =, %ay =9, Yan =<, Yan 1=) 1. The fre/uency of ultrasonic waves is greater than #= 5;G. #. They are highly energetic. . They travel through longer distances. . They are reflected, refracted and a"sor"ed similar to ordinary sound waves. -. $hen ultrasonic waves are passed through li/uid, it produces stationary wave

pattern and ma5es the li/uid to "ehave as an acoustical grating element. 3. 6t produces heating effect. 4. The velocity of Eltrasonic waves depends on the temperature of the medium

throughwhich waves propagate&



9. Eltrasonic waves produce negligi"le diffraction. o they can transmitted over along

distances without apprecia"le loss of energy. <. The speed of Eltrasonic waves depends on fre/uency, it increases with increase of

fre/uency.

1=. They have high penetration depth in solids and li/uids.. $hat is magnetostriction effect& (Yan =3, %ay =4, Yan =9)

$hen an alternating field is applied to a rod of ferromagnetic material such as ic5el,:o"alt, 6ron etc., or Alloys of it, then the rod is thrown into longitudinal vi"rations , there"y producing Eltrasonic waves at resonance. This effect is 5nown as magnetostriction effect.-. $hat are the main differences "etween 7ieGo!electric and magnetostriction method&(Yan <4).O. 76*>O!*J*:TR6: %*T;OD %A*TOTR6:T6O %*T;OD

1. 6t can produce ultrasonic waves of

fre/uency as high as -== %;G

6t can produce ultrasonic waves of fre/uency

a"out %;G only.#. A constant fre/uency can "e o"tained. A constant fre/uency cannot "e o"tained.. 6t has narrow pea5 of resonance. 6t has "road pea5 of resonance.. 2re/uency is independent of

temperature.2re/uency is dependent of temperature.

3. $hat is 7ieGo!electric effect& (%ay =, %ay =4, Yan 1=)$hen pressure or mechanical force is applied along mechanical a'is with respect to optic

a'is of the crystals li5e /uartG, tourmaline, Rochelle salts etc., then e/ual and opposite charges

are produced in electrical a'is with respect to optic a'is of the crystal. This effect is called pieGo!electric effect.4. $hat is inverse pieGo!electric effect& (Yan =3, Yan 1=)

$hen potential difference or e.m.f is applied along electrical a'is with respect to optica'is of the pieGo!electric crystals then the crystal starts vi"rating along mechanical a'is withrespect to optic a'is of the crystals. This effect is called inverse pieGo!electric effect.9. $hat is the principle of OAR& (Or) ;ow can the OAR "e used to find the depthof sea& (Yan =<) OAR is "ased on the echo!sounding of ultrasonic waves. $hen ultrasonic waves is passed towards the proSect in the water, it is reflected and from an echo signal. 0y measuring thetime difference "etween the transmitted and echo signals, the distance of the o"Sect can "ecalculated. The fre/uency of the echo signal is changed due to Doppler effect. This change isfre/uency is used to locate the o"Sect and to determine the velocity and its direction.<. $hy not ultrasonic "e produced "y passing high fre/uency alternating current througha loud spea5er& (ov =#)



1. $hen high fre/uency alternating current is passing through a loud spea5er, inductanceof the spea5er coil "ecomes so high and hence no current passing through it.

#. Joud spea5er coil cannot vi"rate at high fre/uency. Therefore` ultrasonic waves cannot "e produced "y passing high fre/uency alternating current through a loud spea5er.1=. $hat is an acoustic grating& (Or) ;ow is acoustic grating formed& (Yan =<)

$hen ultrasonic waves travel through a transparent li/uid, due to alternating compressionand rarefaction, longitudinal stationary waves are formed in a li/uid. 6f monochromatic lightgrating. uch a grating is 5nown as acoustic grating.

11. $hat is meant "y DT& (Yan =9) on!destructive testing (DT) is the method of testing the material without any

damaging and destroying. 6t is used to e'amine the material and to detect the flaws, defects andother irregularities present in the material without damaging it. 6t is a /uality assurance managingtool, and it gives a good result, safety and relia"ility.1#. $hat are the applications of OAR&

1. 6t is used to locate the shipwrec5s and su"!marines on the "ottom of the sea.#. 6t is used for fish!finding application and the detection of fish shoals.. 6t is useful for all merchant and military ship.. 6t is used for seismic (earth /ua5e) survey.-. 6t is used to find the depth of the sea and, the depth of the roc5s in the sea.

1. ;ow are sound waves classified&ound waves are classified into three categories "ased on fre/uency as follows+

1. 6nfrasonic ("elow #=;G)#. Audi"le sound ("etween #= ;G to #= 5;G). Eltrasonic (a"ove #= 5;G)

1. $hat is sonogram& %ention its application.onogram is an instrument used to monitor and visualiGe the image of the interior parts of

the "ody using high fre/uency sound waves. 6t provides high resolution, high accuracy, and highcontrast ultrasonic images using digital image processing unit.Application+

1. To monitor the interior parts of the "ody more accurately.#. 6t is used to confirm pregnancies and to indicate delivery dates more accurately.. To monitor the health and development of fetus

1-. Define :avitations& %ention its use. (Or) $rite a note on cavitations&

(Yan =<, Yan 1=)$hen the ultrasonic waves propagate through li/uid media, they induce alternative

regions of rarefaction and compression. A negative local pressure at the rarefaction cause local "oiling of the li/uid accompanied "y the "u""le growth and collapse. This phenomenon is5nown as cavitations.Application+

1. 6t is used to accelerate the chemical reactions.



#. 6t is used for ultrasonic cleaning and emulsification.. 6t is used to locate the minerals and oil deposits.

13. ive some of the important industrial applications of ultrasonic& (%ay =9)1. Eltrasonic drilling.#. Eltrasonic welding.. Eltrasonic soldering.. Eltrasonic flaw detection.-. Eltrasonic thic5ness determination.3. Eltrasonic cleaning.

14. $hat are the advantages of ultrasonic cleaning& (Dec #==1, %ay #==9)1. A"le to clean delicate parts without damage.#. A"le to clean small apertures, "lind holes and crevices.. A"le to clean sensitive parts (wiring, plastics)with relatively mild chemistries.. Does not re/uire line!of!sight for effective cleaning.

-. :leaning speed is high and low cost.3. *nvironmentally pollution free and highly safe.

19. %ention any two medical application of ultrasonic. (or) %ention any four uses ofultrasound in clinical medicine. 9(Yan #=1=)

1. 6t is used to detect tumours in human "ody. #. Eltrasonic are used to find velocity of "lood flow and the movement of heart in the

human "ody.. 6t is used for "loodless "rain surgery and painless e'traction of teeth.. 6t is used to measure the internal dimensions of the eye.

1<. Differentiate destructive and non!destructive testing method. (Yan #==9).o Destructive testing on!Destructive testing

1 6t is applied to only a small siGed sample.This is applied to large siGed samples also i.e.,directly on production times.

# amples are damaged during testing.There is no damaged to the sample duringtesting.

Only single test can "e done on one sample.%any num"ers of tests can "e done on thesame sample.

ample preparation is re/uired. o need of ample preparation.- 6t is not used even a single part is in service. 6t can "e used when any part is in service.

3 6t has high time consumption 6t has low time consumption

4 Ja"our cost is very high Ja"our cost is low

#=. ame any four methods of detection of ultrasonic waves. (%ay #==9)1. Thermal method#. 7ieGo!electric method





onogram is a techni/ue which is used to record the sounds produced due to the pumpingaction of the heart using ultrasonic?s. 6t also provides the information on heart ratio, rhythmicity, "lood pumping, valve action, etc.

#9. $hat are the factors affecting the acoustic /uality of a "uilding.• Rever"eration time

• 2ocusing and interference

• *choes and echolen effect

• Resonance

• *'traneous noise

#<. 6f the rever"eration time is lower than the critical value, how will it affect the acoustical/uality of a "uilding.$hen the rever"eration time is lower than the critical value, sound "ecomes inaudi"le "ythe o"server and the sound is said to "e dead and if the rever"eration time is too large,echoes are produced. Therefore, the rever"eration time should have some optimum value.

=. Define rever"eration time of an auditorium.The persistence of audi"le sound, even after the source has stopped to emit the sound iscalled rever"eration. The time during which the sound persists in the hall is called asrever"eration time.

1. Define a"sorption coefficient of a material.The a"sorption coefficient of a material is defined as the ratio of the sound energya"sor"ed "y the surface to that of the total sound energy incident on the surface.

A"sorption coefficient (a) 8

The a"sorption coefficient can also "e defined as the rate of sound energy a"sor"ed "y acertain area of the surface to that of an open window of same area.

#. $rite a note on noise pollution. oise pollution is one of the maSor factor which occurs in our day to day life. The noises produced in a particular area creates harmful effects to the human "eings. 6t producesmental fatigue and irritation. 6t diverts our concentration on wor5 hence reduces theefficiency of the wor5. 6t sometimes affects the nervous system and lowers the restorative/uality of sleep. ome strong noises lead to damage the ear drum and ma5es the wor5erhearing impaired. ;ence noise pollution should "e reduced.

. $hat is loudness& ive the relation "etween loudness and intensity of sound. (or) state$e"er N 2echner law.Joudness of sound is defined as the degree of sensation produced on the ear. This cannot "e measured directly. o that it is measured in terms of intensity. Joudness is proportional to the logarithmic value of intensity.

J log 6



J 8 V log 6This is also 5nown as $e"er N 2echner?s law.

. Define sound intensity level and write its unit.6ntensity level (6J) is e/ual to the difference in loudness, which is given "y

6J 8 J1 ! J= 8 V log1= 61 N log1=6=

$hereas J1 is the loudness of any sound intensity 61 and J= is the loudness correspondingto the standard reference intensity 6=

6J 8 V log1= . Enit for intensity level is "el.

-. %ention any four sound a"sor"ing materials.• $ooden floor

• lass

• :arpets

• 2elt, etc.

3. $e hear sound from a vi"rating "lade. 6f that sound is to "e made louder, what should "edone&The sound from a vi"rating "lade can "e made louder "y the following ways,

• The siGe of the "lade can "e increased.

• A resonant "ody should "e 5ept near the vi"rating "lade.

• 0y removing the sound a"sor"ing material near"y the "lade.

4. $hat is meant "y /uality of sound&The /uality of sound is that characteristic which ena"les us to distinguish "etween two

notes of the same pitch and loudness produced "y two different voices.The loudness and pitch tell us whether it is a voice from a man or a woman. The /ualitywill help us to recogniGe the particular person who is producing the sound without seeinghim.

9. ive the relation "etween loudness and intensity.s.no Joudness 6ntensity1. 6t is degree of sensation produced

in the ear 6t is the energy of sound wave crossing per unit time at right angle to thedirection of propagation

#. 6t is a physiological /uantity 6t is purely physical /uantity

. 6t is difficult to measure 6t can "e easy to measure

<. $hat are the units of loudness& Define loudness.Deci"el+ 6t is the smallest unit compared to "el. 6t is the standard unit to measure theloudness. One deci"el is e/ual to one tenth of "el.7hone+ The measure of loudness in phon of any sound is e/ual to the loudness in deci"elsof an e/ually loud pure tone of fre/uency 1=== ;G





plit of %ar5s M Answer 5ey+%agnetostriction N # %ar5s7ieGo!electric N # %ar5sDiagram F construction N %ar5s$or5ing N # %ar5s

7rinciple N # %ar5sAdvantage F Disadvantages N # %ar5sResonance :ondition N # %ar5s#. *'plain pieGo!electric effect. Descri"e the pieGo!electric method of producing ultrasonicwaves. (Yan 1<<9, %ay #==3, Yan #==9)plit of %ar5s M Answer 5ey+7ieGo!electric N # %ar5sDiagram F construction N %ar5s$or5ing N %ar5s

7rinciple N # %ar5sAdvantage F Disadvantages N # %ar5sResonance :ondition N # %ar5s. $hat is meant "y magnetostriction effect& *'plain with neat s5etch the construction and production of ultrasonic waves using magnetostriction method. (Yan #=1=)plit of %ar5s M Answer 5ey+%agnetostriction N # %ar5s7ieGo!electric N # %ar5sDiagram F construction N %ar5s$or5ing N # %ar5s

7rinciple N # %ar5sAdvantage F Disadvantages N # %ar5sResonance :ondition N # %ar5s. *'plain how ultrasonic waves are produced. *'plain in detail how the ultrasonic pulsetechni/ue is used in OAR. (Yan #==#)plit of %ar5s M Answer 5ey+7roduction of ultrasonic ! 9%ar5sOAR ! 9%ar5s-. (i) $hat is acoustic grating& (ii) Descri"e the method of determining the velocity of ultrasonic waves using acousticalgrating. (iii) %ention any four applications of ultrasonic waves. (Yan #==<, Yan #=1=)plit of %ar5s M Answer 5ey+Acoustic grating N # %ar5sApplications of ultrasonic waves N %ar5sDiagram F construction N %ar5s$or5ing N %ar5s



7rinciple N # %ar5s3. (i) $hat is inverse!pieGo!electric effect& (ii) Descri"e the construction and wor5ing of ultrasonic waves using pieGo!electric method. (iii) tate the merits and demerits of magnetostriction oscillator. (Yan #==<)plit of %ar5s M Answer 5ey+

7ieGo!electric N # %ar5s:onstruction N %ar5s$or5ing N %ar5s7rinciple N # %ar5s%erits and Demerits N %ar5s4. Descri"e with neat diagram the construction of a pieGo!electric generator and how ultrasonicwaves are produced with it. (Yan #=1=)plit of %ar5s M Answer 5ey+Diagram N # %ar5s

:onstruction N %ar5s$or5ing N %ar5s7rinciple N # %ar5sAdvantage F Disadvantages N %ar5sResonance :ondition N # %ar5s9. (i) $hat is pieGo!electric effect& Descri"e the pieGo!electric method of producing ultrasonicwaves. (ii) *'plain how ultrasonic waves are used in the industrial applications of drilling andsoldering. (Yan #=1=)plit of %ar5s M Answer 5ey+

7ieGo!electric effect N # %ar5s:onstruction N %ar5s$or5ing N %ar5s7rinciple N # %ar5sApplications N %ar5s<. (i) Descri"e the process of non!destructive testing of materials using ultrasonic waves "y pulseecho techni/ue. (A N can, 0 N can, : N can). (ii) Discuss in detail how OAR is employed to locate the o"Sects. (Yan #=1=)plit of %ar5s M Answer 5ey+Diagram F construction N %ar5s$or5ing N %ar5s7rinciple N # %ar5sOAR locate the o"Sects N 3 %ar5s1=. 6n ultrasonic DT, $hat are the different scan displays in common use& *'plain. (Yan #==<,Yan #=1=)plit of %ar5s M Answer 5ey+Eltrasonic DT N 3 %ar5s



can displays in common use N 1= %ar5s11. $rite notes on

(i) Detection of ultrasonic. (ii) Eltrasonic welding and cutting.

(iii) $rite short notes on sonograms. (Yan #==<)

plit of %ar5s M Answer 5ey+Detection of ultrasonic N 3 %ar5sEltrasonic welding and cutting N %ar5sDiagram F construction N # %ar5s$or5ing N # %ar5s7rinciple N # %ar5s

1#.Derive an e'pression for rever"eration period of an auditorium and e'plain how this can "eused for determining the a"sor"ing power of surface involved.

calculation rever"eration period

e'pression for growth sound energy N 3%ar5s

e'pression for decay sound energy N 3%ar5s

a"sor"ing power of surface !mar5s

1.$rite the detail a"out the factors affecting the "uildings acoustics and their remedies.

2actors affecting the "uildings ! 3%ar5s

Optimum rever"eration time ! 3%ar5s

Remedies ! %ar5s

1.Discuss the salient point associated with acoustics of auditorium.

rever"eration time ! %ar5s

e'pression for growth sound energy N 3%ar5s e'pression for decay sound energy N 3%ar5s

1-.Discuss the factors rever"eration,resonance,echelon effect,focusing and reflection that affectthe acoustics in hall and the remedies for them.

Rever"eration ! %ar5s



Resonance ! %ar5s

*chelon effect ! %ar5s

2ocusing ! %ar5s

Reflection ! %ar5s

13.what is rever"eration time&Esing sa"ine?s formula e'plain how the sound a"sorptioncoefficient of a material is determined.



e'pression for decay sound energy N 3%ar5s a"sor"ing power of surface !mar5s

13.Derive the e'pression for growth and decay sound energy


*'pression for growth sound energy N 9%ar5s

*'pression for decay sound energy N 9%ar5s

14.i.Define rever"eration time and a"sorption coefficient&

Define for rever"eration time ! #%ar5s

Define for a"sorption coefficient N #%ar5s

ii.Derive sa"ine?s formula for the rever"eration time of a hall


e'pression for decay sound energy N 3%ar5s

19.discuss the factor affecting the acoustics of "uilding and e'plain the factors to "e followed toovercome.



2actors affecting the "uildings ! %ar5s

Optimum rever"eration time ! %ar5s

Remedies ! %ar5s

Joudness !! %ar5s

1<.ive an account of good acoustics property of an auditorium e'plain the remedies for it.

2actors affecting the "uildings ! %ar5

Rever"eration time ! %ar5s

Remedies ! %ar5s

Joudness ! %ar5s

oise !%ar5s



UNIT – V (PHOTONICS AND FIBER OPTICS)


1. $hat is stimulated emission& An atom in the e'cited state is induced to return to ground state there"y resulting in two photons of same fre/uency and energy is called as stimulated emission.

#. $hat is pumping action& 7umping is the process of achieving population inversion i.e., ma5ing more num"er ofatoms in the e'cited state "y supplying energy to the medium is called pumping process. Thereare several methods "y which the population inversion (pumping) can "e achieved.

. $hat are the various methods of achieving population inversion& ome of the commonly used methods are+

• Optical pumping method.• Direct electron e'citation or electric discharge.• 6nelastic atom!atom collision method.• Direct conversion method.• :hemical method.

. $hat is meant "y population inversion& 6n general the num"er of atoms in the ground state will "e more than that of the atoms in

the e'cited state and it is called as usual population. The reverse of this (i.e.) a state of achievingmore num"er of atoms in the higher energy level than that of the lower energy level is called population inversion.

-. tat the properties (or) characteristics of laser "eam& The four important characteristics of the laser "eams are+

• 6t is highly directional• The "eam is purely monochromatic• 6t has high intensity• 6t has coherence

3. $hat are the differences "etween spontaneous and stimulated emission of radiation&

.o. pontaneous emission timulated emission1.

#.

The atom in the e'cited statereturns to ground state there"yemitting a photon, without anye'ternal inducement is called asspontaneous emission.

The emitted photons can move

An atom in the e'cited state isinduced to return to groundstate there"y resulting in two photons of same fre/uency andenergy is called as stimulatedemission.The emitted photons move in





as laser emi conductor laser Ji/uid laser Dye and chemical laser

1. $hat are the conditions re/uired for laser action& (or) Jist the condition to achieve

laser action.The two important conditions re/uired for laser action are+7opulation inversion should "e achievedtimulated emission should "e predominant over spontaneous emission

1-. Distinguish "etween ordinary light and laser "eam.

.o. Ordinary Jight Jaser "eam

1.

#...

-.

3.

6n ordinary light theangular spread is more.

They are not directional.6t is less intense.6t is not a coherent "eamand is not in phase.The radiations are polychromatic*'ample+ unlight,%ercury vapour lamp etc.

6n laser "eam the angularspread is less.They are highlydirectional.6t is highly intense.6t is a coherent "eam andis in phase.The radiations aremonochromatic*'amples+ ;e!e Jaser,:O#Jaser etc

13. $hat is pumping action& aturally, the population inversion is achieved only at negative temperature which is impossi"le.Thus the process "y which population inversion is achieved "y artificial means is called as pumping action.

14. $hat is principle of laser&Due to stimulated emission the photons multiplied "y each step giving rise to an intense

"eam of photons that are coherent and moving in the same direction. ;ence the light is amplified "y stimulated emission of radiation termed as JA*R.

19. $hat is function of ;elium in ;e!e laser&6n ;e!e laser a mi'ture of helium and neon gases under a pressure of =.1mm ;g is used as an

active medium. ;elium atoms are e'cited first "y the interaction with electrons. The e'citedhelium atoms collide in!elastically with neon atoms. The neon atom goes to e'cited state. Thetransition of neon atoms produces a laser light.

1<. $hat are the "asic re/uirements for the laser systems&The three important components of a laser system are+Active medium7umping system









4. $hat is meant "y graded inde' fi"er&

Due to non!uniform refractive indices,their difference in refractive indices "etween the core andthe cladding gradually increases from centre towards interface and hence called graded inde'fi"er.

9. A silica optical fi"er has a core refractive inde' of 1.-= and a cladding refractive inde' of1.4. :alculate the critical angle at the core!cladding interface.

:ritical angle c8 in!1n#Mn1

c8 in!11.4M1.-=849Z11.

<. $hat are active and passive sensors&

Active sensor+

6n intrinsic sensors (or) active sensors the physical parameter to "e sensed directly acts on the

fi"er itself to produce the changes in the transmission characteristics.*'ample+ Temperature M7ressure sensor.

7assive sensor+

6n e'trinsic sensors (or) passive sensors, separating sensing element will "e used and the fi"erwill act as a guiding media to the sensors.

*'ample+ Displacement sensor.

=. $hat are intermodal dispersion&

6nter modal dispersion is defined as pulse spreading caused "y the time delay "etween lower!order modes and higher order modes.


1. 2or atomic transitions, derive *instein relations and hence deduce thee'pressions for the ratio of spontaneous emission rate to the stimulatedemission rate.

plit of %ar5s M Answer 5ey+*instein theory N 13%ar5s#. $ith a neat diagram, e'plain the construction and wor5ing of :O# laser.

plit of %ar5s M Answer 5ey+Diagram N %ar5sApplications N # %ar5s:onstruction N %ar5s$or5ing N %ar5s7rinciple N # %ar5s. 6n ;e!e laser, what is the role of ;e atoms& *'plain the construction and



wor5ing ;e!e laser with the help of energy level diagram.plit of %ar5s M Answer 5ey+Role of ;eliumN # %ar5sDiagram N # %ar5sApplications N # %ar5s:onstruction N %ar5s$or5ing N %ar5s7rinciple N # %ar5s

. $ith a neat diagram e'plain the principle, construction and wor5ing ofsemiconductor laser.

plit of %ar5s M Answer 5ey+;omo Sunction+:onstruction N %ar5s$or5ing N %ar5s

7rinciple N # %ar5s;etero Sunction+:onstruction N %ar5s$or5ing N %ar5s7rinciple N # %ar5s-. (i) Descri"e the construction and wor5ing of d!A laser.plit of %ar5s M Answer 5ey+:onstruction and Diagram N %ar5s$or5ing N %ar5s (ii) *'plain recording and reconstruction of a hologram.plit of %ar5s M Answer 5ey+Recording N %ar5sReconstruction N %ar5s3. Discuss the applications of laser in welding, heat treatment and cutting.plit of %ar5s M Answer 5ey+;eat treatment N %ar5s6nstrumentation techni/ue N %ar5s$elding N %ar5s:utting N %ar5s

4. (i) Define the numerical aperture of an optical fi"er. Derive an e'pression for it. plit of %ar5s M Answer 5ey+Definition, Diagram ! #%ar5sDerivation ! 3%ar5s(ii) *'plain the dou"le cruci"le method of drawing optical fi"er with neat diagram.

plit of %ar5s M Answer 5ey+7rinciple, Diagram and wor5ing ! 3%ar5sAdvantages and Disadvantages ! #%ar5s



9. (i) Discuss the mechanisms of attenuation, dispersion and "ending losses in opticalfi"ers.plit of %ar5s M Answer 5ey+Attenuation Definition with formula ! #%ar5sDiagram F different attenuation mechanisms ! 9%ar5s

(ii) *'plain the principles of wor5ing of temperature and displacement sensors usingoptical fi"ers.plit of %ar5s M Answer 5ey+ensor F its type ! 1%ar5sTemperature and displacement sensor ! -%ar5s

<. (i)*'plain in detail how optical fi"ers are characteriGed according to the material,refractive inde' and modes of propagation.plit of %ar5s M Answer 5ey+:lassification with e'ample(ii) 2ind the refractive inde' of the core and cladding if the A is =. and the relativerefractive inde' difference is .plit of %ar5s M Answer 5ey+2ormula+ n18A #

1=. (i) $hat are different units of fi"er optic communication system& *'plain theirfunctions.plit of %ar5s M Answer 5ey+0loc5 diagram ! %ar5s:omponents F function !9%ar5s(ii) $rite a note on temperature sensor.plit of %ar5s M Answer 5ey+7rinciple, Diagram and wor5ing ! %ar5s

11. *'plain in detail a"out sources and detectors involved in optical fi"ercommunication with necessary diagram.plit of %ar5s M Answer 5ey+J*D ource7rinciple, :onstruction and wor5ing ! 3%ar5sAdvantages and Disadvantages ! #%ar5sDetectors7rinciple, :onstruction and wor5ing ! 9%ar5s

1#. (i) Descri"e a 2i"er optic communication system.plit of %ar5s M Answer 5ey+0loc5 diagram ! #%ar5s

:omponents F function !%ar5s(ii) Descri"e the principle, construction and wor5ing of light emitting diode.plit of %ar5s M Answer 5ey+7rinciple, Diagram and wor5ing of J*D ! 9%ar5s(iii) tate the advantages of light emitting diode in electronic display.plit of %ar5s M Answer 5ey+Advantages ! #%ar5s



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