Question

When light is incident on a metal surface, the maximum kinetic energy of emitted electrons:

• A. Varies with intensity of light
• B. Varies with frequency of light
• C. Varies with speed of light
• D. Varies irregularly

Hint:

Increasing the intensity of light increases the number of photoelectrons but does not change their maximum kinetic energy.

Answer 1

The Correct Option is B

Step 1: {Photoelectric Equation} 
According to Einstein’s photoelectric equation: \[ K_{{max}} = h\nu - W_0 \] where: - \( h \) is Planck’s constant, - \( \nu \) is the frequency of incident light, - \( W_0 \) is the work function of the metal. 
Step 2: {Dependence on Frequency} 
Since \( K_{{max}} \) depends only on \( \nu \) and not on intensity, the correct answer is \( {(B)} \). 
 

Answer 2

Explanation: The maximum kinetic energy of electrons emitted from a metal surface when it is exposed to light is explained by the photoelectric effect, which is a phenomenon where electrons are ejected from a material when it is exposed to light of sufficient frequency. The relation between the maximum kinetic energy (\(K_{\text{max}}\)) of the emitted electrons and the frequency (\(f\)) of the incident light is given by the equation:

K_max = h f - \phi

Where:

• h is Planck's constant.
• f is the frequency of the incident light.
• \(\phi\) is the work function of the metal, which is the minimum energy required to remove an electron from the surface.

From the equation, we see that the maximum kinetic energy of the emitted electrons increases linearly with the frequency of the incident light, provided the frequency is above a certain threshold. This threshold frequency depends on the work function of the specific metal. Therefore, the correct answer is:

Varies with frequency of light.