A : On increasing the temperature , the hight of the peak of the Maxwell curve decreases .
R : The total are under the curve reamins constant for fixed amount of gas.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1)
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4)

Answer

**Step-by-Step Solution:**

1. **Understanding the Maxwell Distribution Curve**: The Maxwell distribution curve represents the distribution of molecular speeds in a gas. The x-axis shows molecular speed (velocity), while the y-axis shows the fraction of molecules with that speed.

2. **Effect of Temperature on the Curve**: When the temperature of the gas increases, the average kinetic energy of the gas molecules also increases. This results in a broader distribution of speeds, meaning that more molecules can achieve higher speeds.

3. **Observation of the Peak**: As the temperature increases, the peak of the Maxwell distribution curve shifts to the right, indicating that the most probable speed of the molecules increases. However, the height of the peak decreases.

4. **Area Under the Curve**: The total area under the Maxwell distribution curve represents the total number of molecules, which remains constant for a fixed amount of gas. Therefore, if the peak height decreases, the curve must spread out to maintain the same area.

5. **Conclusion**: Both the assertion (A) that the height of the peak decreases with increasing temperature, and the reason (R) that the total area under the curve remains constant for a fixed amount of gas, are correct. Thus, the answer is that both A and R are true and R is the correct explanation for A.

**Final Answer**: Both assertion A and reason R are true, and R is the correct explanation for A.

---