Advertisements
Advertisements
Question
Light of intensity ‘I’ and frequency ‘v’ is incident on a photosensitive surface and causes photoelectric emission. What will be the effect on anode current when (ii) the frequency of incident radiation is increased. In each case, all other factors remain the same. Explain, giving justification in each case.
Advertisements
Solution
For photoelectric emission to occur, there is a minimum cut off frequency of the incident radiation called the threshold frequency below which no photoelectric emission occurs. This frequency is independent of the intensity of the incident light. With an increase in the frequency of the incident radiation, the kinetic energy of the photoelectrons ejected increases, whereas it is independent of the number of photoelectrons ejected. Hence, with the increase in the frequency of incident radiation, there will not be any change in the anode current.
APPEARS IN
RELATED QUESTIONS
Write three characteristic features in photoelectric effect that cannot be explained on the basis of wave theory of light, but can be explained only using Einstein's equation.
Light of intensity ‘I’ and frequency ‘v’ is incident on a photosensitive surface and causes photoelectric emission. What will be the effect on anode current when (i) the intensity of light is gradually increased. In each case, all other factors remain the same. Explain, giving justification in each case.
Two monochromatic beams, one red and the other blue, have the same intensity. In which case (i) the number of photons per unit area per second is larger, (ii) the maximum kinetic energy of the photoelectrons is more? Justify your answer.
A photosensitive surface emits photoelectrons when red light falls on it. Will the surface emit photoelectrons when blue light is incident on it? Give reason.
What change will you observe if intensity of incident radiation is changed but the frequency remains the same?
In photoelectric effect, why should the photoelectric current increase as the intensity of monochromatic radiation incident on a photosensitive surface is increased? Explain.
Draw a plot showing the variation of photoelectric current with collector plate potential for two different frequencies, v1 > v2, of incident radiation having the same intensity. In which case will the stopping potential be higher? Justify your answer.
Calculate the momentum of a photon of energy 6 x I 0-19 J.
With reference to the photoelectric effect, what is meant by threshold wavelength?
State how will you use this graph to detennine the value of Planck's constant.
