Intensity of light incident on a photo sensitive surface is doubled. Then

Options

A. A) the number of emitted electrons is tripled
B. B) the number of emitted electrons is doubled
C. C) the K.E. of emitted electrons is doubled
D. D) the momentum of emitted electrons is doubled

Answer

To solve the question regarding the effect of doubling the intensity of light incident on a photosensitive surface, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Intensity and Photoelectric Effect**:
- The intensity of light is defined as the power per unit area. In the context of the photoelectric effect, intensity is related to the number of photons striking the surface per unit time.
- According to the photoelectric effect, when light of sufficient frequency hits a photosensitive surface, it can eject electrons from that surface.

2. **Relationship Between Intensity and Number of Electrons**:
- The number of emitted electrons is directly proportional to the intensity of the incident light. This means that if the intensity increases, the number of emitted electrons also increases.
- Mathematically, if \( I \) is the intensity and \( N \) is the number of emitted electrons, we can express this as:
\[ N \propto I \]

3. **Doubling the Intensity**:
- If the intensity of light is doubled (i.e., \( I' = 2I \)), we can substitute this into our proportional relationship:
\[ N' \propto I' = 2I \]
- This implies that the number of emitted electrons \( N' \) will also double:
\[ N' = 2N \]

4. **Conclusion**:
- Therefore, when the intensity of light incident on the photosensitive surface is doubled, the number of emitted electrons is also doubled.

5. **Selecting the Correct Option**:
- From the options provided:
- Option A: The number of emitted electrons is tripled.
- Option B: The number of emitted electrons is doubled. (Correct)
- Option C: The kinetic energy of emitted electrons is doubled.
- Option D: The momentum of emitted electrons is doubled.
- The correct answer is **Option B**.

### Final Answer:
When the intensity of light incident on a photosensitive surface is doubled, the number of emitted electrons is doubled (Option B).