Download Class 9

Modern Physics
(PC300)
Class #9: Introductory Stuff towards
Quantum Mechanics
Quantum Homework Questions
Photoelectric
Also some from
Thornton and Rex–
Due Wednesday
"Yeah, well I got mine first
Experimental basis for the introduction of a quantum theory.
Photoelectric Effect – Almost done
X-Ray Production
Charge/mass of an electron
Blackbody Radiation
Stefan-Boltzmann law
Wien’s Displacement Law
Ultraviolet Catastrophe
Review what we know about how gamma particles are absorbed by matter.
Photoelectric effect
Compton Scattering
Pair Production
Photoelectric Effect
+
-
1 2
 mv   eV0
2
max
Photoelectric Effect: Intensity
Photoelectric Effect: Frequency
1902: Lenard - Maximum KE does not depend on intensity
1905 Lenard - Nobel Prize
Photoelectric Effect: Work
Functions
(Kmax)
1 2
 mv   eV0  hf  
2
 max
Various Work Functions
http://www.youtube.com/watch?v=m55kgyApYrY
1923 Millikan - Nobel Prize
Lab – Photoelectric Effect
X Ray Production
1901 Roentgen - Nobel Prize
EM Spectrum: X-Rays
(Duane-Hunt Rule)
min 
hc 1
e V0
X Ray Production
1897 - J.J.Thompson
1906 - Nobel Prize
Measuring charge/mass (e/m)
Electron beam
Cathode Ray
e
2V
 2 2
m R B
Cathode Ray Tube
Derive in lab
Lab ? - e/m setup
1909 - Robert Millikan
Precise Measurement of e
Oil Drop Experiment
Black Body Radiation
“An idealized object that absorbs all the electromagnetic radiation falling on it,
regardless of frequency.”
Early observations – hot metals
Ultraviolet Catastrophe
Classical Physics – Rayleigh-Jeans Law
u( f , T )  8kT
4
1900 - Planck’s Law
Unusual (Crick-Watson) type approach:
-> Equation that fits data
-> Make it work
-> Could not justify finding
1918 Planck - Nobel Prize
Lab – Blackbody Radiation
Extension - Pasco Setup