Assertion : If U.V radiations and infrared radiations fall on a metal plate, stopping potential would be grater for infrared radiations.
Reason : Maximum kinetic energy of photoelectrons is inversely proportional to the frequency of incident radiation.

Options

A. If both assertion and reason are correct and reason is a correct explanation of the assertion.
B. If both assertion and reason are correct but reason is not the correct explanation of assertion.
C. If assertion is correct but reason is incorrect
D. If both assertion and reason are incorrect.

Answer

To solve the given question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that if UV and infrared radiations fall on a metal plate, the stopping potential would be greater for infrared radiations.
- Stopping potential (V) is related to the maximum kinetic energy (K.E.) of the emitted photoelectrons, which is given by the equation:
\[ K.E. = h\nu - h\nu_0 \]
where \(h\) is Planck's constant, \(\nu\) is the frequency of the incident radiation, and \(\nu_0\) is the threshold frequency.

2. **Analyzing the Energies of UV and Infrared**:
- UV radiation has a higher frequency than infrared radiation. Since energy is directly proportional to frequency (\(E = h\nu\)), UV radiation has more energy than infrared radiation.
- Therefore, when UV radiation is incident on the metal plate, it will produce photoelectrons with greater kinetic energy compared to infrared radiation.

3. **Conclusion on the Assertion**:
- Since the stopping potential is greater for radiation with higher energy (higher frequency), the assertion that stopping potential would be greater for infrared radiations is **incorrect**.

4. **Understanding the Reason**:
- The reason states that the maximum kinetic energy of photoelectrons is inversely proportional to the frequency of incident radiation.
- This statement is incorrect. The correct relationship is that the maximum kinetic energy of photoelectrons is **directly proportional** to the frequency of the incident radiation, as shown in the equation above.

5. **Conclusion on the Reason**:
- Since the reason is also incorrect, we conclude that both the assertion and the reason are false.

### Final Answer:
Both the assertion and the reason are incorrect.