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Robert Millikan 1868-1953 Nobel Prize in Physics 1923
"for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect"
"for his work on the elementary charge of electricity and on the photoelectric effect"
Albert Einstein 1879-1955 Nobel Prize in Physics 1921
Max Planck 1858-1947 Nobel Prize in Physics 1918
Emission and Absorption of Light evidence for quantization
"in recognition of the services he rendered to the advancement of Physics by his discovery of energy quanta".
Wilhelm Wien
Wilhelm Wien (18643-1928) Nobel Prize 1911
Example of Black Body Spectra for different temperatures
A “reasonable” example of a black body
Diagram of Millikan’s Device For measuring photoelectric effect
Data from Millikan’s 1916 Article
Phys. Rev. 7, 355–388 (1916)
Example Problem The work functions for K and Zn are 2.26 eV and 4.24 eV Which will emit photoelectrons when illuminated by Red, Blue and UV light?
Wavelength K (2.26 eV) Zn (4.24 eV)
Red (700 nm)
Blue (400 nm)
UV (280 nm)
E=hn-w=0 hc=1240eV nm Energy of photon is hn or hc/l or 1240 eV nm/ l
Example Problem The work functions for K and Zn are 2.26 eV and 4.24 eV Which will emit photoelectrons when illuminated by Red, Blue and UV light?
Wavelength K (2.26 eV) Zn (4.24 eV)
Red (700 nm)
Blue (400 nm)
UV (280 nm)
E=hn-w=0 hc=1240eV nm Energy of photon is hn or hc/l or 1240 eV nm/ l
Plug in for Red, Blue, UV ?
Photon Photoelectron? E= hc/l If (hc/l- w) > 0
Example Problem The work functions for K and Zn are 2.26 eV and 4.24 eV Which will emit photoelectrons when illuminated by Red, Blue and UV light?
Wavelength K (2.26 eV) Zn (4.24 eV)
Red (700 nm) 1.77 eV
Blue (400 nm) 3.10 eV
UV (280 nm) 4.42 eV
E=hn-w=0 hc=1240eV nm Energy of photon is hn or hc/l or 1240 eV nm/ l
Plug in for Red, Blue, UV ?
Photon Photoelectron? E= hc/l If (hc/l- w) > 0
Example Problem The work functions for K and Zn are 2.26 eV and 4.24 eV Which will emit photoelectrons when illuminated by Red, Blue and UV light?
Wavelength K (2.26 eV) Zn (4.24 eV)
Red (700 nm) 1.77 eV NO NO
Blue (400 nm) 3.10 eV YES NO
UV (280 nm) 4.42 eV YES YES
E=hn-w=0 hc=1240eV nm Energy of photon is hn or hc/l or 1240 eV nm/ l
Plug in for Red, Blue, UV ?
Photon Photoelectron? E= hc/l If (hc/l- w) > 0
