Answers for Ch. 5 A + B (Part I)Answers for Ch. 5 A + B (Part I)Part A1) 42) 33) 34) 15) 46) 47) 18) 29) 410) 311) 4

Part B12) 3.2 m13) 23 m/s14) 300 m/s15) 12.7 m/s16) 16.56 m17) 14.3 m18) There was a decrease in flight time, a 45° always produces the greatest range19) 34.6 m/s

20) H

oriz

onta

l Spe

ed

Time

Modern PhysicsModern Physics

Regents PhysicsRegents Physics

Mr. RockensiesMr. Rockensies

Quantum TheoryQuantum TheoryWhat is Quantum Theory?

1) Proposed by Max Planck in 1900.

2) States: “atoms absorb or emit light in discrete amounts called Quanta or Photons.”

3) Photon – a “particle” of light carrying energy & momentum.

a) Energy: Ephoton = h f or Ephoton = h c λ

Ephoton = energy of a photon λ = wavelengthh = Planck’s constant c = speed of light in a vacuumf = frequency of light = 3.0 x 108 m/s

b) Photon – Particle Collisions (collision between photon & electron)I. Photon energy and momentum decreasesII. Particle energy and momentum increasesIII. Energy and momentum are conserved

4) Matter Wavesa) proposed by deBroglie in 1924b) moving particles have wave

properties only when particles are on a subatomic scale (electrons, protons, neutrons)

c) λ = h p

λ = wavelength of subatomic particle

h = Planck’s constantp = momentum of subatomic

particle

Example: What is the matter wavelength of an electron with a speed of 2.0 x 106 m/s?

λ = h pλ = 6.62 x 10-34 J·s (2.0 x 106 m/s)(9.1 x 10-31 kg)λ = 3.6 x 10-10 m

MODELS OF THE MODELS OF THE ATOMATOM

HOW DID THE STRUCTURE OF HOW DID THE STRUCTURE OF THE ATOM EVOLVE?THE ATOM EVOLVE?

Rutherford’s Model Experiment Rutherford’s Model Experiment (1911)(1911)

The detecting screen was illuminated with a flash of light every time an alpha particle hit it.

Rutherford’s ConclusionsRutherford’s Conclusions

1)1 % of alpha particles deflected into hyperbolic paths 99% of alpha particles passed through foil2)most of the atom is empty space3)positive charge and mass of atom is concentrated in

a small dense core called the nucleus.

Rutherford’s atom

Bohr’s Model (1913)Bohr’s Model (1913)

Bohr’s model agreed with what Rutherford had said two years previously, but added on certain distinctions

1) electrons move in orbits, shells, or energy levels around the nucleus and can move from one energy level to another.

2) Energy Level Diagramsa) each atom of a particular element has what is called an energy level diagramb) shows the energy levels or states of an atom

Bohr’s Model of the Atom

Energy Level DiagramsEnergy Level Diagrams1) Ground State

• electron is in its lowest energy level• atom is most stable• electron has least amount of energy2) Excited State• electron jumps to a higher energy

level• atom is less stable• electron has more energy3) Ionization Level• atom is “ionized” when electron is

removed from atom• Ionization energy – energy needed

to remove an electron from atom** Signs indicate the energy the atom

lacks to become ionized when in that state

Results of Absorption/EmissionResults of Absorption/EmissionABSORPTION EMISSION

atoms absorb energy by absorbing energy of both colliding:1)electrons (electrical energy)2)photons (light energy)

atoms release energy in the form of photons (light)

Absorption/Emission Spectrum

How do we predict the colors an How do we predict the colors an element will give off?element will give off?

On the reference table: Ephoton (electron) = Ei - Ef

Ephoton (electron) = energy of photon absorbed or released by atomOR

energy of electron absorbed by atom

Ei = initial energy of electron in the atomEf = final energy of electron in the atom•If we know the energy of the photon, we can then use E = hf to find the frequency of that photon.•If we know the frequency, then we can use our reference tables to look up the corresponding color.•We could also calculate wavelength using c = fλ

What color is the photon?What color is the photon?1. An electron is excited to the 3rd energy level, n=3, and then

drops back down to n=2. How much energy is given off by the atom when the electron falls down?

2. What is the frequency of the photon being emitted?3. What is the wavelength of that photon?4. What is the color of that photon?Ephoton = Ei – Ef

Ephoton = -1.51 eV – (-3.40 eV)Ephoton = 1.89 eV (must convert to J)Ephoton = hf3.02x10-19 J =(6.63x10-34 J•s)ff = 4.56x1014 Hz c = fλ3x108 m/s =(4.56x1014 Hz)λλ = 6.58x10-7 mColor on reference table: Red

1 eV = 1.6x10-19J

Cloud ModelCloud Model

States that there is no specific orbit for an electron as it moves about the nucleus. Instead, there is a region of most probable electron location called an electron cloud.

Atomic SpectraAtomic SpectraEmission/Bright line SpectrumEmission/Bright line Spectrum

How do we see the How do we see the emission/bright line spectrum?emission/bright line spectrum?

gas discharge tube with Xenon gas

colored light is passed through

Spectroscope(contains a prism)

Emission Spectrum for Xenon

Emission SpectrumEmission Spectrum1. A series of bright lines of color on a black background2. Unique for each element (can be used to identify an

element)3. Each line of color corresponds to an energy level change

for an electron and a wavelength emitted by the material

Absorption/Emission Spectrum

Absorption SpectrumAbsorption Spectrum1. A series of dark lines on a bright background2. A characteristic set of light wavelengths absorbed by a

material

Einstein’s Mass-Energy Einstein’s Mass-Energy RelationshipsRelationships

What is Einstein’s Theory of What is Einstein’s Theory of Relativity?Relativity?

1.A mass, m, is equivalent to an amount of energy, E2.As an equation – E = mc2

Where: E = Energy equivalent in Joulesm = mass of 1 atomic mass unit (a.m.u.) in kg

**1 a.m.u. = 1.66x10-27 kg**c = speed of light in air/vacuum

This equation eventually led to the creation of this

(nuke)

What is the Energy Equivalent What is the Energy Equivalent of 1 a.m.u. (Proton or Neutron)?of 1 a.m.u. (Proton or Neutron)?

E = mc2

E = (1.66x10-27 kg)(3.0x108 m/s)2

E = 1.49x10-10 JoulesE = 9.31x108 eV = 931MeV

million electron-volts1 a.m.u. = 9.31x102 or 931 MeV

**Conversion factor on Reference Table**

Example #1Example #1

Example #2Example #2

Example #3Example #3

Example #4Example #4

Example #5Example #5

Fundamental ForcesFundamental ForcesWhat are the four fundamental What are the four fundamental

forces in order from strongest to forces in order from strongest to weakest?weakest?

Strong ForceStrong Force

1)Nuclear Force which holds a nucleus of an atom together against the enormous forces of repulsion of the protons

2)Short Ranged – range is 10-15 meters (diameter of a medium sized nucleus

Electromagnetic ForceElectromagnetic Force1)Manifests itself through the forces between

charges and the magnetic force2)Can be attractive or repulsive3)Long Ranged – range is infinite

Weak ForceWeak Force1)Involved in many decays of nuclear particles2)Responsible for the fusion of the Sun and the

conversion of neutrons to protons in the nuclei3)Short Ranged – range is 10-17 meters

GravityGravity1) A purely attractive force which acts along the

line joining the centers of mass of the two masses

2) The forces on the 2 masses are equal in size, but opposite in direction, obeying Newton’s 3rd Law

3) Long Ranged – range is infinite

Classification of MatterClassification of Matter

How is all matter classified?How is all matter classified?

The Standard ModelThe Standard ModelAll MatterAll Matter

Baryons(Very Heavy)

Leptons (Light)Hadrons (Heavy)

Mesons (Medium Heavy)

Made of 3 quarks Made of 1 quark and 1 anti-quark

There are a total of 6 quarks (flavors)

-up, down, charm, strange, top, bottom

There are also 6 anti-quarks

There are also 6 Leptons

- electron, electron-neutrino, muon, muon-neutrino, tau, tau-neutrino

There are also 6 anti-Leptons

Bosons – The Four Fundamental Bosons – The Four Fundamental Force CarriersForce Carriers

Strong ForceStrong Force gluongluon ggWeak ForceWeak Force W bosonW bosonElectric ForceElectric Force photonphoton γγGravity ForceGravity Force gravitongraviton GG

-Never detected-Never detected

Common BaryonsCommon Baryons

ProtonProton pp uuduudAnti-protonAnti-proton pp ūūdūūdNeutronNeutron nn udduddOmegaOmega ΩΩ ssssss

Common MesonsCommon Mesons

PionPion ππ++ ududAnti-pionAnti-pion ππ-- ūdūdKaonKaon k-k- sūsū

Conservation Laws still applyConservation Laws still apply

1)1) Mass/Energy - the total amount of mass Mass/Energy - the total amount of mass and energy equivalent of mass (E=mc^2) and energy equivalent of mass (E=mc^2) is constantis constant

2)2) MomentumMomentum

3)3) ChargeCharge

4)4) Quantization of Charge (quarks)Quantization of Charge (quarks)