Question

Which figure shows the correct variation of applied potential difference (\(V\)) with photoelectric current (\(I\)) at two different intensities of light (\(I_1<I_2\)) of same wavelengths:

• A.
• B.
• C.
• D.

Hint:

In the photoelectric effect, the stopping potential is independent of intensity and depends only on the frequency of the incident light. The saturation current increases with intensity.

Answer 1

The Correct Option is C

Step 1: {Understanding the Photoelectric Effect} 
- The photoelectric effect involves the emission of electrons from a metal surface when light of a certain frequency (or wavelength) strikes it. The key observation is that the energy of the emitted electrons depends on the frequency (or wavelength) of the incident light, not its intensity. 
- The stopping potential is the minimum voltage required to stop the most energetic emitted electrons. It is independent of the light intensity but depends on the wavelength (or frequency) of the incident light. This means that the stopping potential remains the same for different intensities of light, as long as the frequency (or wavelength) is the same. 
- The saturation current, however, increases with the intensity of the incident light. This is because a higher intensity means more photons are hitting the surface, and more electrons are being emitted. The saturation current represents the maximum current that can be obtained when all emitted electrons are collected. 
Step 2: {Interpreting the Graphs} 
- In the graph representing the photoelectric effect, the x-axis typically represents the wavelength (or frequency) of the incident light, and the y-axis represents the stopping potential or the saturation current. 
- The correct graph for this situation should show that the stopping potential is the same for both intensities of light, as it is independent of intensity. However, the saturation current will be higher for \( I_2 \) than for \( I_1 \), because \( I_2 \) corresponds to a higher intensity, which results in more electrons being emitted from the surface. Thus, the correct graph is (C).