Light of frequency 1.5 times the threshold frequency is incident on a photosensitive material, photo electric current is emitted. If the frequency of light is halved and intensity is doubled, the photoelectric current becomes

Options

A. 4 times the original current
B. 2 times the original current
C. half the original current
D. zero

Answer

To solve the problem, we need to analyze the situation step by step based on the given information about the photoelectric effect.

### Step-by-Step Solution:

1. **Understanding the Threshold Frequency**:
- The threshold frequency (\( f_0 \)) is the minimum frequency of light required to emit photoelectrons from a photosensitive material.
- In this case, the incident light has a frequency of \( f = 1.5 f_0 \).

2. **Initial Condition**:
- Since the frequency of the incident light is greater than the threshold frequency, photoelectrons are emitted, resulting in a photoelectric current.

3. **Changing the Frequency**:
- The problem states that the frequency of light is halved. Therefore, the new frequency \( f' \) is:
\[ f' = \frac{f}{2} = \frac{1.5 f_0}{2} = 0.75 f_0 \]

4. **Comparing with Threshold Frequency**:
- Now, we compare the new frequency \( f' \) with the threshold frequency \( f_0 \):
\[ f' = 0.75 f_0 < f_0 \]
- This means that the new frequency is less than the threshold frequency.

5. **Effect on Photoelectric Current**:
- According to the photoelectric effect, if the frequency of the incident light is less than the threshold frequency, no photoelectrons will be emitted.
- Therefore, the photoelectric current will be zero.

6. **Considering Intensity**:
- The intensity of light is doubled, but since the frequency is below the threshold, this change in intensity does not affect the emission of photoelectrons.
- Hence, the photoelectric current remains zero regardless of the intensity.

### Final Answer:
The photoelectric current becomes **zero**.