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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.
,3,2,1,0 nnhfE
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.
oo Whf J 0
maxKE
Hz1014.1
sJ106.626
eVJ1060.1eV 73.4 1534
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.
m102.1
sm100.6kg101.9
sJ1063.6 10631
34
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
