Physics 264L
Monday 2015-10-05
Today’s Goal: Establish Experimentally That
E=hf
p=h/l
For All Particles (Electrons, Photons, etc)
Discussion: Feynman’s 1964 Video on
Quantum Mechanical View of Nature
Points of Interest, Confusion?
Interference of Coherent Waves
In the Double-Slit Experiment
Interference of Coherent Waves
In the Double-Slit Experiment
Waves at slits have to be coherent for
interference to occur! Two different
light bulbs in front of each slit will
not give interference pattern.
Diffraction Grating:
Many Equally Spaced Coherent Sources
Interference of Light from Soap Bubble Skin: Two
Reflected Waves From Outer, Inner Surfaes
Diffraction: Light Interference by Edges
Floaters
Light Passing Through a Circular Aperture
Is Blurred by Diffraction
Light passing through a circular aperture of diameter D is spread by diffraction into
a wider circular beam of light with a bright central intensity maximum surrounded
by alternating rings of destructive (dark) and constructive (bright) interference. If
we choose to define the size of the central bright intensity maximum by where the
first dark ring occurs, then the angular width of the central intensity maximum is 2
where =1.22 l/D is given by the above Rayleigh formula. Roughly speaking, the
angular spread is of order 2l/D, twice the ratio of wavelength to aperture diameter.
Two-Slit Experiment With Electrons II
Tonomura 2005
Two-Slit Experiment With Electrons I
Tonomura et al
“Demonstration of single-electron buildup of
an interference pattern”, A. Tonomura et al,
American J. Physics 57(2):117 (1989)
Tonomura Single-Electron Detector
“Demonstration of single-electron buildup of an interference
pattern”, A. Tonomura et al, American J. Physics 57(2):117 (1989)
Two-Slit Experiments Done With
Buckminsterfullerene C60, See Interference!
Establishing that E = h f
Photoelectric Experiment of Lenard
Stopping Voltage Versus Intensity I
And Versus Frequency f