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What is Photo Electric Effect & its derivation explained by Albert Einstein. |
This question has been answered earlier... According to Plank's quantum theory, light is emitted from a source in
the forms of bundles of energy called photons. Energy of each photon is .
Einstein made use of this theory to explain how photo electric emission
takes place.
According to Einstein, when photons of energy fall on a metal
surface, they transfer their energy to the electrons of metal. When the
energy of photon is larger than the minimum energy required by the
electrons to leave the metal surface, the emission of electrons take
place instantaneously.
He proposed that an electron absorbs one whole photon or none. The
chance that an electron may absorb more then one electron is negligible
because the number of photons is much lower than the electron. After
absorbing the photon, an electron either leaves the surface or
dissipates its energy within the metal in such a short interval that it
has almost no chance to absorb second photon. An increase in intensity
of light source simply increases the number of photon and the number of
photo electrons but no increase in the energy of photo electron.
However, increase in frequency increases the energy of photons and photo
electrons.
According to Einstein's explanation of photoelectric emission, a
photon of energy 'E' performs two operations:
1. Removes the electron from the surface of metal
2. Supplies some part of energy to move photo electron towards anode
Since minimum amount of energy to remove electron from a surface is
equal to work function, we can write Einstein equation as:
Energy Supplied = Energy Consumed in ejecting an electron + maximum
Kinetic energy of electron. Equations from (1) to (6) are known as Einstein's photoelectric equations |