Assertion: The change in air pressure effects the speed of sound.
Reason: The speed of sound in gases is proportional to the square of pressure.

Options

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

Explanation

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

### Step 1: Understand the Assertion
The assertion states: "The change in air pressure affects the speed of sound."

- According to the principles of physics, the speed of sound in a gas is influenced by several factors, including temperature and the properties of the gas. However, when considering the effect of pressure alone, we find that the speed of sound does not change significantly with pressure in an ideal gas, as long as the temperature remains constant.

### Step 2: Understand the Reason
The reason states: "The speed of sound in gases is proportional to the square of pressure."

- The formula for the speed of sound in a gas is given by:
\[ V = \sqrt{\frac{\gamma P}{\rho}} \]
where \( V \) is the speed of sound, \( \gamma \) is the adiabatic constant, \( P \) is the pressure, and \( \rho \) is the density of the gas. While it is true that speed can be expressed in terms of pressure, it is essential to note that as pressure increases, density also increases, and the ratio of \( P/\rho \) remains constant under isothermal conditions. Thus, the speed of sound is effectively independent of pressure.

### Step 3: Conclusion
- Since the assertion is incorrect (the change in air pressure does not affect the speed of sound significantly), and the reason is also misleading (the speed of sound is not directly proportional to the square of pressure in practical terms), we conclude that both the assertion and the reason are false.

### Final Answer
Both the assertion and reason are false.

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