Thin LensesThin Lenses

91 is the highest grade while 75 is 91 is the highest grade while 75 is the lowest grade.the lowest grade.

Best Project ( Website and Best Project ( Website and Reflection Paper).......allReflection Paper).......all

Best Portfolio...... Best Portfolio......

Lecture fom MirrorLecture fom Mirror

From what material are curve From what material are curve mirrors made from?mirrors made from?

How plane and curve mirrors How plane and curve mirrors formed images?formed images?

What are the types of curved What are the types of curved mirrors?mirrors?

State the mirror and magnification State the mirror and magnification equation use to locate an image in equation use to locate an image in curved mirrors.curved mirrors.

What is prism?What is prism?

Light going through a Light going through a prism bends toward the prism bends toward the basebase

n1n2

n =11Bending angle depends on value of n2

n1

Refraction in PrismsRefraction in Prisms

Two prisms base to base

If we apply the laws of refraction to two prisms, the rays bend toward the base, converging light.

Parallel rays, however, do not converge to a focus leaving images distorted and unclear.

Refraction in Prisms Refraction in Prisms (Cont.)(Cont.)

Two prisms apex to apex

Similarly, inverted prisms cause parallel light rays to bend toward the base (away from the center).

Again there is no clear virtual focus, and once again, images are distorted and unclear.

Lenses?Lenses?

What is a lens?What is a lens?

A transparent object that refracts A transparent object that refracts light rays, causing them to light rays, causing them to converge or diverge to create an converge or diverge to create an imageimage

Types of Converging Types of Converging LensesLenses

In order for a lens to converge light it must be thicker near the In order for a lens to converge light it must be thicker near the midpoint to allow more bending.midpoint to allow more bending.

Double-convex Double-convex lenslens

Plano-convex Plano-convex lenslens

Converging Converging meniscus lens meniscus lens

Types of Diverging Types of Diverging LensesLenses

In order for a lens to diverge light it must be thinner near the In order for a lens to diverge light it must be thinner near the midpoint to allow more bending.midpoint to allow more bending.

Double-concave Double-concave lenslens

Plano-concave Plano-concave lenslens

diverging meniscus diverging meniscus lens lens

Converging LensesConverging Lenses

A converging lens is thicker at the A converging lens is thicker at the middle than it is at the rimmiddle than it is at the rim– The front of the lens is the side of The front of the lens is the side of

the lens where the object isthe lens where the object is

Converging lenses can produce Converging lenses can produce real or virtual imagesreal or virtual images

Converging LensesConverging Lenses

The focal points are equidistant from the center of the lens. That distanceis the focal length of the lens.

F F 2 F2 F

Converging Lens Converging Lens Reference Rays Reference Rays

RayRay From object From object to lensto lens

From lens to From lens to imageimage

Parallel RayParallel Ray Parallel to Parallel to principal axisprincipal axis

Passes Passes through focal through focal point Fpoint F

Central RayCentral Ray To the center To the center of the lensof the lens

From the From the center of the center of the lenslens

Focal rayFocal ray Passes Passes through focal through focal point Fpoint F

Parallel to Parallel to principal axisprincipal axis

Converging LensesConverging Lenses

The focal points are equidistant from the center of the lens. That distanceis the focal length of the lens.

F F 2 F2 F

Ray 1

Ray 2

Ray 3

Images Created by Converging LensesImages Created by Converging Lenses

Images produced by lenses Images produced by lenses

An object An object infinitely far infinitely far away from a away from a converging lens converging lens will create a will create a point image at point image at the focal pointthe focal point– i.e. light from i.e. light from

the Sunthe Sun

Images produced by lenses Images produced by lenses

As a distant object As a distant object approaches the focal approaches the focal point, the image point, the image becomes larger and becomes larger and farther awayfarther away

Images produced by lenses Images produced by lenses

When the When the object is at the object is at the focal point, the focal point, the light rays exit light rays exit parallel to each parallel to each other and the other and the image is “at image is “at infinity”infinity”– i.e. a lighthouse i.e. a lighthouse

or a searchlightor a searchlight

Images produced by lenses Images produced by lenses

When the object is inside the When the object is inside the focal point, the rays are drawn focal point, the rays are drawn the same way but you must the same way but you must extend them backwards in order extend them backwards in order to find the imageto find the image

Converging Lens: Objects inside the Converging Lens: Objects inside the focal pointfocal point

F F 2 F2 F

These rays are diverging and won’t cross

Draw lines extending backwards to form the image

SummarySummary

Object Object positionposition

Image Image PositionPosition

Real or Real or virtualvirtual

Magnified Magnified or or

diminisheddiminished

Inverted or Inverted or erecterect

>2F>2F

at 2Fat 2F

between 2F between 2F and Fand F

at Fat F

between F between F and lensand lens

between F and 2F

at 2F

> 2F

at infinity

same side as object

virtual

real

real

real

magnified

magnified

same size

diminished

upright

inverted

inverted

inverted

DivergingDiverging ConvergingConverging2.

Locate and describe the image below

Seatwork 1 (Lecture Seatwork 1 (Lecture Note)Note)

1. A converging lens has a focal length of 17 cm. A candle is located 48 cm from the lens. What type of image will be formed, and where will it be located?

2.2. A plano-convex lens of focal length 5.0 cm is A plano-convex lens of focal length 5.0 cm is used in reading lamp to focus light from a used in reading lamp to focus light from a bulb on a book. If the lens is 60.0 cm from bulb on a book. If the lens is 60.0 cm from the book, how far should it be from bulb’s the book, how far should it be from bulb’s filaments?filaments?

3.3. A toy of height A toy of height 8.4 cm8.4 cm is balanced in front of is balanced in front of a converging lens. An inverted, real image a converging lens. An inverted, real image of height of height 23 cm23 cm is noticed on the other side is noticed on the other side of the lens. What is the magnification of the of the lens. What is the magnification of the lens?lens?

2727

• The focal length of particular lens depends both on the index of refraction n of its material relative to that of the medium it is in and on the radii of curvature R1 and R2 .

1/f = (n-1) ( 1/R1 + 1/R2)

• R is + if the surface is convex.

• R is – if the surface is concave.

• f is + for converging lens

• f is negative for diverging lens

• It does not matter which surface is considered as1 and 2.

A meniscus lens has a convex A meniscus lens has a convex surface whoe radius of curvature surface whoe radius of curvature is 25 cm and a concave surface is 25 cm and a concave surface whose radius of curvature is 15 whose radius of curvature is 15 cm. The index of rafraction is cm. The index of rafraction is 1.52. Find the focal length of the 1.52. Find the focal length of the lens and wether it is converging lens and wether it is converging or diverging.or diverging.

Thin Lens and Thin Lens and Magnification Equations Magnification Equations

fqp

111

p

qM

Sign conventions for Sign conventions for lenses lenses

++pp Object distance for Object distance for

lenseslenses

qq Image in back of Image in back of the lens ( real)the lens ( real)

Image in front Image in front of the lens of the lens (virtual)(virtual)

ff Converging LensConverging Lens Diverging LensDiverging Lens

Sample Problem Sample Problem

Sherlock Holmes examines a clue Sherlock Holmes examines a clue by holding his magnifying glass by holding his magnifying glass (with a focal length of 15.0 cm) (with a focal length of 15.0 cm) 10.cm away from an object. Find 10.cm away from an object. Find the image distance and the the image distance and the magnification. Describe the magnification. Describe the image he observes. Draw a ray image he observes. Draw a ray diagram to confirm your answers.diagram to confirm your answers.

What kind of lens is a What kind of lens is a magnifying glass?magnifying glass?

Magnifying glasses produce Magnifying glasses produce enlarged images. Therefore, a enlarged images. Therefore, a magnifying glass is a converging magnifying glass is a converging lens. lens.

f = + 15 cm, p= +10 cmf = + 15 cm, p= +10 cm

Solve the problemSolve the problem

30

1

10

1

15

1111

pfq cm 30q

310

30

cm

cm

p

qM

The image is virtual and upright

Magnifying Lens Ray DiagramMagnifying Lens Ray Diagram

F F 2 F2 FObject

Notice that the image is located at 2F (30 cm) and it is also in front of the lens which is why q is negative.

Diverging LensesDiverging Lenses

A diverging lens is thinner at the A diverging lens is thinner at the middle than it is at the rimmiddle than it is at the rim

A diverging lens has two focal A diverging lens has two focal points but only one focal lengthpoints but only one focal length

Diverging lenses only produce Diverging lenses only produce virtual imagesvirtual images

Diverging LensesDiverging Lenses

The focal points are equidistant from the center of the lens. That distanceis the focal length of the lens.

F F 2 F2 F

Diverging Lens Reference Rays Diverging Lens Reference Rays

RayRay From object From object to lensto lens

From lens to From lens to imageimage

Parallel RayParallel Ray Parallel to Parallel to principal axisprincipal axis

Directed away Directed away from focal from focal point Fpoint F

Central RayCentral Ray To the center To the center of the lensof the lens

From the From the center of the center of the lenslens

Focal rayFocal ray Proceeding Proceeding toward back toward back focal point, Ffocal point, F

Parallel to Parallel to principal axisprincipal axis

Drawing the RaysDrawing the Rays

F F 2 F2 F

Ray 1

Ray 2

Ray 3

Sample Problem (p.579 Sample Problem (p.579 #1)#1)

Using a ray diagram, find the Using a ray diagram, find the position and height of an image position and height of an image produced by a viewfinder in a produced by a viewfinder in a camera with a focal length of 5.0 camera with a focal length of 5.0 cm if the object is 1.0 cm tall and cm if the object is 1.0 cm tall and 10.0 cm in front of the lens. A 10.0 cm in front of the lens. A camera viewfinder is a diverging camera viewfinder is a diverging lens.lens.

Ray DiagramRay Diagram

F F 2 F2 F

Object

The image is about 1/3 of the object height (.33 cm). The image location is about 3 or 4 cm from the lens. So, q is approximately -3.5 cm.

Smart people verify!Smart people verify!

10

3

10

1

5

1111

pfqcmq 3.3

p

q

h

hM

o

i

cmcm

cmcm

p

qhh o

i 33.10

)33.3(1)(

Group 1 Human EyesGroup 1 Human Eyes

a. Identify and describe the parts of the human eye vital in seeing objects.

b. Describe how image is formed in the retina ( Ray diagram is needed).

c. Explain how the eye accommodates to see clearly both far and near objects.

Group 2 CameraGroup 2 Camera

a. Identify and describe the parts of the camera.b. Describe how image is formed in the camera (Ray diagram is needed)c. Similarities and differences of the camera and the human eye.

Group 3 Vision DefectsGroup 3 Vision Defects

a. Myopia and its Causes and corrective lens (w/ ray diagrams)b. Hyperopia eyes and its Causes and

corrective lens (w/ ray diagrams)c. Presbyopia eyes and its Causes and

corrective lens (w/ ray diagrams)d. Astigmatism eyes its causes and corrective

lens (w/ ray diagrams)

Group 4 MicroscopeGroup 4 Microscope

a.a. Parts of the microscope and its Parts of the microscope and its function.function.

b.b. Image formation in objective and Image formation in objective and eyepiece lens w/ ray diagramseyepiece lens w/ ray diagrams

Group 5 TelescopeGroup 5 Telescope

a.a. Parts of the telescope and its Parts of the telescope and its function.function.

b.b. Image formation in objective and Image formation in objective and eyepiece lens w/ ray diagramseyepiece lens w/ ray diagrams

Group 6 Group 6 Different Optical Different Optical InstrumentInstrument

Picture and its uses / function/sPicture and its uses / function/sa.a. PeriscopePeriscopeb.b. EndoscopeEndoscopec.c. InterferometerInterferometerd.d. SpectrometerSpectrometere.e. SunglassesSunglasses