# Doppler's Effect: Apperent change in frequency

Please see the attachment.

I have a test today and this question was on my old test . but I want to know how to solve other scenarios like this. ( I made up some questions below )

A stationary observer hears a frequency of 500Hz while the source is moving directly toward him. If he hears a frequency of 400Hz when the source is moving directly away from him, what is the speed of the source? (assume that the speed of sound is 344 m/s)

My question:

Same question but the frequency are not given but the speed of source moving toward listener is 35 m/s and when source is moving away from observer speed is at 20 m/s. find both frequency's (observer is still stationary)?

How about if the source is stationary but listener is not and has the same speed as the source did?

How about if we had the similar question but the observer is not stationary and is moving directly toward the source that has a 500Hz frequency. If he hears a frequency of 400 Hz when he is moving directly away from the source, what is the speed of the observer/listener?

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#### Solution Preview

Please see the attachment.

I have a test today and this question was on my old test . but I want to know how to solve other scenarios like this. ( I made up some questions below )

A stationary observer hears a frequency of 500Hz while the source is moving directly toward him. If he hears a frequency of 400Hz when the source is moving directly away from him, what is the speed of the source? (assume that the speed of sound is 344 m/s)

How about if we had the similar question but the observer is not stationary and is moving directly toward the source that has a 500Hz frequency. If he hears a frequency of 400 Hz when he is moving directly away from the source, what is the speed of the observer/listener?

Few Points to remember about Doppler's effect

1. If the source is moving towards the listener wavelength of the sound produced in air ...

#### Solution Summary

The frequency of sound is calculated for moving source and all other situations are discussed.