Question

Light of incident frequency 2 times the threshold frequency is incident on a photosensitive material. If the incident frequency is made \( \frac{1}{3} \)rd and intensity is doubled then the photoelectric current will

• A. decrease.
• B. increase.
• C. be halved.
• D. be zero.

Hint:

In the photoelectric effect, the frequency of the incident light must be above the threshold frequency to emit photoelectrons. Increasing intensity alone cannot produce a current if the frequency is below the threshold.

Answer 1

The Correct Option is D

Step 1: Understanding the photoelectric effect.
The photoelectric current depends on both the frequency of the incident light and its intensity. The photoelectric effect only occurs if the frequency of the incident light is greater than the threshold frequency.
Step 2: Frequency and intensity effects.
- If the incident frequency is reduced to \( \frac{1}{3} \) of its original value, the frequency is below the threshold frequency, which means no photoelectrons will be emitted, and the photoelectric current will be zero. - Doubling the intensity does not help because the frequency is the key factor in the emission of photoelectrons.
Step 3: Conclusion.
Since the frequency is below the threshold, the correct answer is (D), the photoelectric current will be zero.