According to Newton, when a wave passes through a gas, changes taking place in pressure and volume of air are

Options

A. isothermal
B. isobaric
C. isochoric
D. adiabatic

Answer

To solve the question regarding the changes in pressure and volume of air when a wave passes through a gas according to Newton, we can follow these steps:

### Step 1: Understand the Nature of Sound Waves
When a sound wave travels through a gas (like air), it creates regions of compression and rarefaction. Compression refers to areas where air molecules are pushed closer together, resulting in higher pressure, while rarefaction refers to areas where air molecules are spread apart, leading to lower pressure.

**Hint:** Remember that sound waves consist of alternating high-pressure and low-pressure regions.

### Step 2: Identify the Process Described by Newton
Newton proposed that the changes in pressure and volume during the propagation of sound waves occur under constant temperature conditions. This means that he considered the process to be isothermal, where the product of pressure (P) and volume (V) remains constant (PV = constant).

**Hint:** Recall that isothermal processes occur at constant temperature.

### Step 3: Analyze the Validity of Newton’s Assumption
While Newton's assumption of an isothermal process was initially accepted, it was later challenged. The rapid nature of sound wave propagation means that the process is not slow enough to maintain constant temperature. Instead, it involves quick changes that do not allow for heat exchange with the surroundings.

**Hint:** Think about how quickly sound travels and how that affects temperature changes.

### Step 4: Introduce Laplace's Correction
Laplace pointed out that the process is not isothermal but rather adiabatic. In an adiabatic process, there is no heat exchange with the environment, and the temperature can change due to the rapid compression and rarefaction of air molecules.

**Hint:** Remember that adiabatic processes involve rapid changes where heat does not flow in or out.

### Step 5: Conclusion
Thus, according to Newton, the changes taking place in pressure and volume of air when a wave passes through it are considered isothermal. However, with Laplace's correction, it is more accurately described as an adiabatic process.

**Final Answer:** According to Newton, when a wave passes through a gas, the changes taking place in pressure and volume of air are isothermal, but with Laplace's correction, they are adiabatic.

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