Question

Light from a bulb is falling on a wooden table but no photoelectrons are emitted as:

Answer 1

Hint: The photoelectric emission generally occurs when light with the threshold frequency incidence in some metal surfaces. If the minimum energy of the electron is known as a work function, then the electron can come out from the surface. The difference between the work function of a wooden surface and a metal surface has to be known to answer this question. Note that the electron can not emit if it does not gain the minimum energy.

Complete answer:
When light with a suitable wavelength or frequency is incident on a metal surface, an electron emits from the surface with energy – this is the Photoelectric emission.
This is suitable or it can be said this minimum frequency is called the Threshold frequency. And, the minimum energy that the electron gains during emission is called the work function. The work function only depends upon the metallic surface, not upon the process of how the electron gains energy. The work function is measured in the eV unit.
Light from a bulb when it falls on a wooden table no photoelectric emission occurs because the electron does not gain the energy that is just across the range of the energy of the wooden surface and, therefore, the electron can not come out from this particular surface. That means the work function of a wood is always greater than the incident photons.
But for metal, since the work function is less than the incident photon, during emission the electron gains the minimum energy to come out from this surface.

Note: The photoelectric current is directly proportional to the intensity of the incident light. The highest velocity or the kinetic energy of the electrons does not depend upon the intensity of the incident light but is directly proportional to the frequency of that light. It also does not depend upon the temperature of the metal.
The photoelectric current is not gained if the frequency of the incident light is less than the threshold one. The threshold frequency is different for the different metals.
After the emission, the metallic surface becomes positively charged with very little range. This principle is used for making Photo-voltaic cells.