# I with the Doppler Effect - I solved 2/3 parts of the problem

• mmutinoi
In summary, Jane hears a frequency of 467.5 Hz, John is running at a speed of 5.45 m/s, and there is a 12 dB difference in sound level between them.
mmutinoi
I solved for parts and a and b of this problem and need someone to check the answers for me and help me with part c.
A) 467.5 Hz
B) 5.45 m/s

Jane is standing on the platform waiting for the train. The train approaching the platform from the north at 20 m/s blows its whistle when it is 100 m away from Jane. John, running towards the platform from south, is 50 m away from Jane when the whistle is blown. The frequency of the whistle when the train is at rest is 440 Hz, and the speed of sound in air is 340 m/s.

a) What frequency of sound does Jane hear?
b) John hears a frequency of 475 Hz. How fast is he running?
c) What is the difference in sound level between Jane and John assuming the whistle to be a point source of sound?

A) 467.5 HzB) 5.45 m/sC) The difference in sound level between Jane and John is determined by the inverse-square law of sound, which states that the intensity of sound decreases in proportion to the square of the distance from the source. Therefore, the difference in sound level can be calculated as: Sound Level Jane - Sound Level John = 10 log(100^2 / 50^2) = 10 log(4) = 12 dB

## What is the Doppler Effect?

The Doppler Effect is a phenomenon where the frequency and wavelength of a wave appear to change when the source of the wave is moving relative to the observer. This results in a shift in the perceived frequency or pitch of the wave.

## How does the Doppler Effect affect sound waves?

The Doppler Effect affects sound waves by changing the perceived frequency of the wave. When a sound source is moving toward an observer, the frequency is compressed, making the pitch sound higher. When the source is moving away, the frequency is stretched, making the pitch sound lower.

## What is the difference between the Doppler Effect for light waves and sound waves?

The main difference between the Doppler Effect for light waves and sound waves is the speed at which they travel. Light waves travel much faster than sound waves, so the change in frequency is more noticeable for light. Additionally, the Doppler Effect for light waves has been used to measure the speed and distance of stars and galaxies, while the Doppler Effect for sound waves is used more in practical applications such as police radar.

## How is the Doppler Effect used in everyday life?

The Doppler Effect is used in everyday life in various ways. For example, it is used in police radar to measure the speed of moving vehicles. It is also used in medical ultrasound technology to measure the flow of blood in the body. Additionally, the Doppler Effect is used in weather radar to track and predict the movement of storms and other weather patterns.

## What are the limitations of the Doppler Effect?

One limitation of the Doppler Effect is that it only applies to waves that are emitted from a source that is moving. It does not work for stationary sources. Additionally, the Doppler Effect can only measure the relative velocity between the source and the observer, not the absolute velocity. Finally, the accuracy of the measurements can be affected by factors such as interference or reflections of the waves.

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