Assertion : When temperature of a body is increased, in radiant energy, number of low wavelength photons get increased.
Reason : According to Wien's displacement law `lambda_m prop 1/T`.

Options

A. If both Assertion and Reason are true and the Reason is correct explanation of the Assertion.
B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C. If Assertion is true, but the Reason is false.
D. If Assertion is false but the Reason is true.

Answer

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

### Step 1: Understand the Assertion
The assertion states that when the temperature of a body is increased, the number of low wavelength photons in the radiant energy increases.

**Explanation**: As the temperature of a body rises, it emits radiation more intensely and shifts towards shorter wavelengths. This means that the energy of the emitted photons increases, leading to a greater number of photons with lower wavelengths.

### Step 2: Understand the Reason
The reason given is based on Wien's displacement law, which states that the wavelength (λ_m) corresponding to the maximum intensity of radiation emitted by a black body is inversely proportional to the temperature (T) of the body, expressed as:
\[ \lambda_m \propto \frac{1}{T} \]

**Explanation**: According to this law, as the temperature (T) increases, the maximum wavelength (λ_m) decreases. This implies that the peak of the emitted radiation moves towards shorter wavelengths (higher energy photons).

### Step 3: Connect the Assertion and Reason
Now we need to connect the assertion with the reason.

- As the temperature increases, according to Wien's law, the peak wavelength of emitted radiation decreases.
- A decrease in peak wavelength means that there is an increase in the number of photons emitted at lower wavelengths.

### Step 4: Conclusion
Both the assertion and the reason are true, and the reason correctly explains the assertion. Therefore, the correct conclusion is that both the assertion and reason are true, and the reason is the correct explanation for the assertion.

### Final Answer
Both the assertion and the reason are true, and the reason is the correct explanation for the assertion.

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