Physics 264LMonday 2015-10-05

Today’s Goal: Establish Experimentally That E = h f

p = h / 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 ApertureIs 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 /D is given by the above Rayleigh formula. Roughly speaking, the angular spread is of order 2/D, twice the ratio of wavelength to aperture diameter.

Two-Slit Experiment With Electrons IITonomura 2005

Two-Slit Experiment With Electrons ITonomura 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 WithBuckminsterfullerene C60, See Interference!

Establishing that E = h fPhotoelectric Experiment of Lenard

Stopping Voltage Versus Intensity I And Versus Frequency f