Phot diodes are preferable used in reverse bias conditions for measuring light intensity because

Options

A. Current in reverse biase is less which is easier to measure compared to higher currents in forward bias
B. High fractional change due to photo effects in minority carrier dominated reverse bias current is more easily measurable than the high ractional change in the forward bias current
C. Low fractional change due to photo-effect in minority carries dominated reverse bias current is more easily measurable than the high fractional change in the forward bias current
D. Current in zero in reverse bias set-up

Explanation

### Step-by-Step Solution:

1. **Understanding Photodiodes**:
- Photodiodes are semiconductor devices that convert light energy into electrical energy. They are designed to detect light and generate a current proportional to the intensity of the light.

2. **Structure of a Photodiode**:
- A photodiode consists of a p-n junction, which has a depletion region where charge carriers (electrons and holes) are absent. The p-side has an abundance of holes (positive charge carriers), while the n-side has an abundance of electrons (negative charge carriers).

3. **Depletion Region and Built-in Electric Field**:
- In the depletion region, there exists a built-in electric field due to the separation of charges. This electric field allows for the movement of thermally generated electron-hole pairs across the junction when no external voltage is applied.

4. **Reverse Bias Condition**:
- When the photodiode is reverse biased (the p-side is connected to the negative terminal and the n-side to the positive terminal of a battery), the electric field in the depletion region is enhanced. This increases the mobility of minority charge carriers (electrons in the p-side and holes in the n-side).

5. **Minority Current Generation**:
- The reverse bias condition leads to the generation of a small current known as the minority current, which is due to the movement of these minority charge carriers. This current is very small under normal conditions.

6. **Effect of Light on Photodiode**:
- When light falls on the photodiode, it generates additional electron-hole pairs in the depletion region. This increase in charge carriers alters the minority current.

7. **Detecting Light Intensity**:
- The change in the current due to the generation of additional electron-hole pairs can be easily detected. The strength of this current is proportional to the intensity of the incident light, making photodiodes effective for measuring light intensity in reverse bias conditions.

8. **Conclusion**:
- Therefore, photodiodes are preferably used in reverse bias conditions for measuring light intensity because this configuration enhances the detection sensitivity and allows for a clear measurement of changes in light intensity.