Chapter 29 Particles and Waves. 29.1 Wave Particle Duality When a beam of electrons is used in a...

Chapter 29

Particles and Waves

29.1 Wave Particle Duality

When a beam of electrons is used in aYoung’s double slit experiment, a fringepattern occurs, indicating interference effects.

Waves can exhibit particle-like characteristics,and particles can exhibit wave-like characteristics.

29.2 Blackbody Radiation and Planck’s Constant

All bodies, no matter how hot or cold,continuously radiate electromagnetic waves.

Electromagnetic energy isquantized.

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sJ10626.6 34 hPlanck’sconstant

frequency

29.3 Photons and the Photoelectric Effect

Electromagnetic waves are composed of particle-likeentities called photons.

hfE hp

29.3 Photons and the Photoelectric Effect

Experimental evidence that light consistsof photons comes from a phenomenoncalled the photoelectric effect.

29.3 Photons and the Photoelectric Effect

When light shines on a metal, a photon can give up its energy to an electronin that metal. The minimum energy required to remove the least strongly held electrons is called the work function.

electroneject toneededwork

Minimum

electron ejected ofenergy kinetic

Maximum

max

energyPhoton

KE oWhf

29.3 Photons and the Photoelectric Effect

electroneject toneededwork

MinimumenergyPhoton

electron ejected ofenergy kinetic

Maximum

maxKE oWhf

29.3 Photons and the Photoelectric Effect

Example 2 The Photoelectric Effect for a Silver Surface

The work function for a silver surface is 4.73 eV. Find the minimumfrequency that light must have to eject electrons from the surface.

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maxKE

Hz1014.1

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19

h

Wf oo

29.3 Photons and the Photoelectric Effect

29.3 Photons and the Photoelectric Effect

29.4 The Momentum of a Photon and the Compton Effect

The scattered photon and the recoil electron depart thecollision in different directions.

Due to conservation of energy,the scattered photon must havea smaller frequency.

This is called the Compton effect.

29.4 The Momentum of a Photon and the Compton Effect

Momentum and energy areconserved in the collision.

cos1mc

h

29.5 The de Broglie Wavelength and the Wave Nature of Matter

The wavelength of a particle is given by the same relation that applies to a photon:

ph

de Broglie wavelength

29.5 The de Broglie Wavelength and the Wave Nature of Matter

Neutron diffraction is a manifestation of the wave-like propertiesof particles.

29.5 The de Broglie Wavelength and the Wave Nature of Matter

Example 5 The de Broglie Wavelength of an Electron and a Baseball

Determine the de Broglie wavelength of (a) an electron moving at a speed of 6.0x106 m/s and (b) a baseball (mass = 0.15 kg) moving at a speedof 13 m/s.

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sm100.6kg101.9

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ph

m103.3

sm13kg 15.0

sJ1063.6 3434

ph

29.5 The de Broglie Wavelength and the Wave Nature of Matter

Particles are waves of probability.

29.6 The Heisenberg Uncertainty Principle

THE HEISENBERG UNCERTAINTY PRINCIPLE

Momentum and position

4

hypy

Uncertainty in y componentof the particle’s momentum

Uncertainty in particle’sposition along the y direction

29.6 The Heisenberg Uncertainty Principle

THE HEISENBERG UNCERTAINTY PRINCIPLE

Energy and time

4

htE

Uncertainty in the energyof a particle when the particleis in a certain state

time interval during which the particle is in that state