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Old Aug 15th 2008, 10:26 PM   #1
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Photoelectric effect

Striking a beam of monochromatic light on metal, why the velocity of fastest electrons are independent of light intensity, is that higher the light intensity, more the energy supplied and hence higher velocity?

What other factors would affect the velocity of electrons in photoelectric effect?
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Old Aug 17th 2008, 05:21 PM   #2
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Originally Posted by werehk View Post
Striking a beam of monochromatic light on metal, why the velocity of fastest electrons are independent of light intensity, is that higher the light intensity, more the energy supplied and hence higher velocity?

What other factors would affect the velocity of electrons in photoelectric effect?
The key is that the electrons can only be "bumped" out of the metal when the light is at certain frequencies. (Thanks to the Bohr atom structure. This is part of the work function of the metal.) So the energy the electrons come off at is independent of any wavelength lower than this incident light energy. A greater intensity of light will only produce more electrons (more atoms get hit by the light), so the kinetic energy of the electrons can only come from the frequency of the light.

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