Statement-I : A p-n junction with reverse bias can be used as a photodiode to measure light intensity.
Statement-II : In a reverse bias condition the current in small but it is more sensitive to changes in incident light intensity.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion.
B. if both assertion and reason are true but reason is not the correct expalanation of the assertion
C. if assertion is true , but reason is false
D. both assertion and reason are false statements.

Answer

To solve the problem, we need to analyze both statements provided in the question regarding the p-n junction and its use as a photodiode.

### Step-by-Step Solution:

1. **Understanding Photodiodes:**
A photodiode is a semiconductor device that converts light energy into electrical energy. It operates on the principle of the photoelectric effect, where photons (light particles) are absorbed by the semiconductor material, generating electron-hole pairs.

**Hint:** Recall that photodiodes are specifically designed to detect light and convert it into an electrical signal.

2. **Reverse Bias Condition:**
In a reverse bias configuration, the p-n junction is connected in such a way that the p-type material is connected to the negative terminal of the power supply, and the n-type material is connected to the positive terminal. This increases the depletion region and reduces the current flow under normal conditions.

**Hint:** Understand how reverse bias affects the depletion region and the flow of current in a p-n junction.

3. **Sensitivity to Light:**
When light (photons) strikes the photodiode in reverse bias, it can generate electron-hole pairs. Although the current in reverse bias is small, the photodiode is sensitive to changes in light intensity. A small change in light intensity can lead to a noticeable change in the current due to the high sensitivity of the device.

**Hint:** Consider how the generation of electron-hole pairs in response to light affects the current in the circuit.

4. **Analyzing the Statements:**
- **Statement I:** A p-n junction with reverse bias can be used as a photodiode to measure light intensity. This is true because photodiodes operate in reverse bias to detect light.
- **Statement II:** In a reverse bias condition, the current is small but it is more sensitive to changes in incident light intensity. This is also true, as the sensitivity of the photodiode allows it to detect small variations in light.

**Hint:** Evaluate whether each statement is true or false based on the principles of photodiodes and their operation.

5. **Conclusion:**
Both statements are correct, and Statement II provides a correct explanation for Statement I. Therefore, the correct conclusion is that both statements are true, and Statement II explains Statement I.

**Final Answer:** Both Statement I and Statement II are correct, and Statement II is the correct explanation of Statement I.