DOPPLER EFFECT – EXERCISES

In this part you will solve more complicated tasks than those in Questions section. Try to solve each excercise generally at first and then substitute the numbers to the general solution.

Exercise 1

The car is moving on the road with speed 72 km/h. The car has the alarm sound witched on with the frequency 4 000 Hz and the car is passing around one man. What frequencies will the man hear during approaching and receding the car? Calculate with sound velocity 340 m/s.

4250 Hz; 3778 Hz

4500 Hz, 3500 Hz

5000 Hz, 3000 Hz

Exercise 2

Observer, which is hearing car horn, has a feeling that sound is higher by major second while the car is coming closer than the car is moving out(f₁/f₂ = 9:8). Calculate the speed of car. Calculate with sound velocity 340 m/s..

60 m/s

40 m/s

20 m/s

Exercise 3

Derive general relation for spectral lines extension in the case of rotating star. You know the radius of the star R and its angular speedω. Calculate the width of spectral line Δλ, which had wavelength λ₀.

Δλ = Rωλ₀/c

Δλ = 2Rωλ₀/c

Δλ = 2Rωc/λ₀

Exercise 4

What speed for car is needed for drivers argumentation thah he saw green light instead of the red one. Calculate with wavelengths 530 nm and 630 nm for green color and red color respectively.

320 km/h

~0.1 speed of light

~0.166 speed of light