Chapter 27, Problem 38A

To determine

To explain: Einstein’s photon theory which says that light below the threshold frequency of a metal produces no photoelectrons, regardless of the intensity of the light.

Explanation of Solution

Introduction:

  $E=h\upsilon$

where $E$ is energy of photons, $h$ is plank’s constant and $\upsilon$ is frequency.

Emission of photoelectrons takes place when energy of incident light photons is greater than or equal to work function and emission of photoelectrons does not depend on intensity of incident photon.

For photoemission to take place, energy of incident light photons is greater than or equal to work function of the metal. From the formula $E=h\upsilon$ , you can say that energy of photons depends on frequency of photons. The minimum frequency at which energy photon is equal to work function is called threshold frequency. If frequency of incident photons is less than threshold frequency energy of photon and energy of photon is less than work function ,so electron will not emit.

Conclusion:

Work function is minimum energy which is required for photo emission. It depends on frequency of photon. It does not depend on the number of photon incident.