Man tossing hot and cold water balloons
(thermal infrared!)
School Blocks YouTube? Click on video link below
B) Einstein explains photoelectric effect
1) Light intensity and electron emission explained.
| Photons are received individually | |
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| Each photon emits e - | |
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Light emitted as particles
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Bright Light
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Dim Light |
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(Lots of photons) |
(few photons) |
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High Frequency Light |
Low Frequency Light |
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(High Energy Photons) |
(Low Energy Photons) |
Brightness (Intensity) - measure of # of photons emitted.
Frequency measure of
energy of light
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Photon Energy = 5 eV |
KE = 2 eV |
**eV - electron volts - unit of energy
How much work did this photon have to do to remove the electron?
Answer: 3 eV
What would happen if a photon
of 2 eV hit the same metal?
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| Photon Energy = 5 eV | KE = 2 eV |
Photon would not have enough energy to emit an electron
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| Photon Energy = 5 eV | KE = 2 eV |
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