Question

In photoelectric effect, the photo current

• A. does not depend on the frequency of photon but depends on intensity of incident light.
• B. decreases with Increase in frequency of incident photon.
• C. increases with increase in frequency of incident photon.
• D. depends with on intensity of incident radiation and its frequency.

Hint:

Remember this direct pairing for the photoelectric effect: Intensity controls the quantity (photoelectric current), while Frequency controls the quality or energy (stopping potential / kinetic energy).

Answer 1

The Correct Option is A

Step 1: Understanding the Question:
The problem asks about the dependencies of the photo current produced during the photoelectric effect with respect to the frequency and intensity of the incoming light radiation.

Step 2: Key Formula or Approach:
According to Einstein's photoelectric equation, the frequency ($f$) of incident light determines the maximum kinetic energy of the emitted photoelectrons, provided it exceeds the threshold frequency ($f_0$).
The intensity of light determines the number of photons striking the photosensitive surface per unit time.
$$\text{Photoelectric Current} \propto \text{Number of photoelectrons emitted/sec} \propto \text{Intensity of incident light}$$

Step 3: Detailed Explanation:
When the frequency of incident light is greater than the threshold frequency, electron emission occurs instantly.
Increasing the intensity of the light beam increases the total number of photons striking the metal surface per second. Since one photon interacts with exactly one electron, a higher intensity leads to a larger number of ejected electrons per second. This directly increases the magnitude of the photo current.
Conversely, changing the frequency of the light (while remaining above $f_0$) changes only the individual kinetic energy of each escaping electron, leaving the total number of escaping charges per second completely unchanged. Therefore, above the threshold limit, the photo current is independent of the light's frequency.

Step 4: Final Answer:
The photo current does not depend on the frequency of the photon but depends on the intensity of the incident light, which corresponds exactly to option (A).