9.4 The Doppler Effect

Question 1

What is the doppler effect?

Answer 1

The change in the observed frequency of a wave whenever there is a relative motion between the emitter and the receiver.

Question 2

What are some applications of the Doppler effect?

Answer 2

Determining the speed of a car

Determining the speed of blood cells in an artery.

Question 3

What is the equation for the doppler effect for the source moving towards the observer?

Answer 3

f0 = fs (v/(v-vs))

where f0 is the observed frequency
fs is the source of the frequency
v is the wave speed
vs is the speed of the source

Question 4

What is the equation for the doppler effect for the source moving away from the observer?

Answer 4

f0 = fs (v/(v+vs))

where f0 is the observed frequency
fs is the source of the frequency
v is the wave speed
vs is the speed of the source

Question 5

What is the equation for the doppler effect for the observer moving towards the observer?

Answer 5

f0 = fs(v+v0/v)

where f0 is the observed frequency
fs is the source of the frequency
v is the wave speed
v0 is the speed of the observer

Question 6

What is the equation for the doppler effect for the observer moving away from the observer?

Answer 6

f0 = fs(v-v0/v)

where f0 is the observed frequency
fs is the source of the frequency
v is the wave speed
v0 is the speed of the observer

Question 7

What is the red shift?

Answer 7

A shift of received light to a longer wavelength (lower frequency) than that emitted.

Question 8

What is the blue shift?

Answer 8

A shift of received light to a shorter wavelength (higher frequency) than that emitted.

Question 9

If the speed of the source is small compared to the speed of light what is the approximate formula?

Answer 9

delta lambda/lambda = v/c
where delta lambda = lambda’ - lambda

where delta lambda is the shift in wavelength
lambda is the wavelength emitted at the source, lambda ‘ is the observed wavelength, v is the speed of the source and c is the speed of light.