Why is the photoelectric effect not possible at all the frequencies?
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Solution
Step 1: Photoelectric effect
In the photoelectric effect, when a beam of light of a particular frequency is incident on the surface of a metal, the electrons are emitted from the surface of the metal.
The threshold frequency is the minimum required frequency for photoelectric emission.
For values smaller than threshold frequency the effect is not possible regardless of the intensity of incident light.
An illustrative diagram of the photoelectric effect is shown below.
Step 2: Reason for particular frequencies for Photoelectric effect
The frequency of incident light must be equal to or greater than the threshold frequency for the photoelectric effect.
For frequency smaller than the threshold frequency, the photoelectric emission of electrons is not possible.
There will be an emission of photoelectron if the photon frequency is precisely equal to the threshold frequency, but the kinetic energy of the electrons emitted will be negligible.
It can be inferred from the above image that,
As the frequency of red light is lower than the metal's threshold frequency, the photoelectric effect does not occur when it touches the metallic surface.
When green light hits a metallic surface, photoelectrons are released, causing the photoelectric effect.
When blue light hits a metallic surface, the photoelectric effect occurs and the kinetic energy of the photoelectrons released by blue light is substantially higher than those of green light because blue light has a higher frequency than green light.
Hence, the photoelectric effect is not possible for all frequencies because a certain minimum frequency is required for the photoelectric effect to take place.
