Photoelectric Effect - Conceptual Problems - 02

Photoelectric Effect

What is threshold frequency?

The threshold frequency (vo) is the minimum frequency of the incident light, for which photoemission is possible, from a given metal surface. It equals (Wo/h), where Wo  is the work function of the metal concerned

Does threshold frequency depends on the nature of the emitter?

Ans Yes ,each emitting surface has a threshold frequency characteristic of the ‘emitter’ concerned.

What is stopping potential?

Ans The minimum value of the negative potential needed, to completely stop the flow of the photoelectric current, is known as the stopping potential. It depends on the frequency of the incident light, for a given emitter.

The stopping potential for some material is 1.2 V. What is the energy range of the emitted photoelectrons?

The range of energies of the emitted photoelectrons will be from 0 to 1.2 eV.

The intensity of incident radiations in a photoelectric experiment is doubled. How the stopping is potential affected?

The stopping potential will remain unaffected because it does not depend on the intensity of the incident light

If the intensity of the incident radiation in a photocell is increased, how does the stopping potential vary?

Stopping potential is directly proportional to frequency of the incident radiations only. So, stopping potential remain unaffected by increase in intensity of incident radiation.

If the intensity of the incident radiation on a metal is doubled, what happens to the kinetic energy of the emitted photoelectrons?

There is no change in the kinetic energy of the emitted electrons. This K E. is independent of the intensity of the incident radiation as long as its frequency remains the same.

The frequency of incident radiation is greater than threshold frequency in a photocell. How will the stopping potential vary if frequency is increased, keeping other factors constant?

Stopping potential will get increased.

The wavelength of electromagnetic radiation is doubled. What will happen to the energy of
the photons?

Thus, on doubling the wavelength, the energy of the photons will be halved.

Is photoelectric effect an instantaneous phenomenon” ?
Yes, the photoelectric effect is an instantaneous phenomenon with (practically) no time delay between the incidence of light and the start of the photoelectric emission.

Note: Few of the above questions are similar. They are here to show the variations of  language in different sets of question papers.