A bell is ringing inside of a sealed glass jar that is connected to a vacuum pump. Initially, the jar is filled with air, What does one hear as the air is slowly removed from the jar by the pump?

Options

A. The sound intensity from the bell gradually decreases
B. The frequency of the sound from the bell gradually increases.
C. The frequency of the sound from the bell gradually decreases. (
D. The speed of the sound from the bell gradually increases.

Answer

To solve the problem, we need to understand the relationship between sound, air, and the process of creating a vacuum in the jar.

### Step-by-Step Solution:

1. **Understanding Sound Propagation**:
Sound is a mechanical wave that requires a medium (like air) to travel. In the case of the bell ringing inside the jar, the sound waves generated by the bell travel through the air inside the jar.

**Hint**: Remember that sound needs a medium to propagate. What happens when you change the medium?

2. **Initial Condition**:
When the jar is filled with air, the bell rings, and the sound is transmitted through the air. At this point, we can hear the bell clearly.

**Hint**: Consider how sound travels in air. What do you hear when the bell rings in normal conditions?

3. **Using the Vacuum Pump**:
As the vacuum pump removes air from the jar, the density of the air inside the jar decreases. This reduction in air density affects the propagation of sound waves.

**Hint**: Think about how the absence of air affects sound. Does sound travel better in denser or less dense mediums?

4. **Decrease in Sound Intensity**:
As air is gradually removed, the intensity of the sound waves decreases. This is because fewer air molecules are available to transmit the sound waves, leading to a reduction in the sound's loudness.

**Hint**: How does the number of particles in a medium affect sound transmission?

5. **Final Observation**:
Eventually, as more air is removed and the vacuum increases, the sound becomes fainter and may eventually become inaudible. However, initially, you will hear the bell ringing, but it will gradually become quieter.

**Hint**: What happens to the sound as the medium becomes less effective at transmitting it?

### Conclusion:
As the air is slowly removed from the jar by the pump, one hears the sound of the bell gradually decreasing in intensity until it becomes very faint or inaudible.

### Final Answer:
The sound intensity of the bell will start decreasing gradually as the air is removed from the jar.