How can I use the doppler effect equation?

Question

Aibling6n2re · Accepted Answer

Explanation:Suppose that an ambulance is travelling at 30 m/s towards a stationary observer at an accident scene and emits a siren of sound wave frequency 400 Hz. Calculate the frequency that the observer hears. Take the speed of sound in air as 340 m/s.Solution:      f    ′    =  f  (            v      +              v                  0                            v      −              v                  s                      )  =  400  (            340      +      0              340      −      30        )=438,71 Hz

Karissa Sosa · Accepted Answer

Suppose an observer in a spacecraft travels at a speed of 2x10^8 m/s towards a stationary red light emitting light of wavelength 660 nm. Calculate the frequency and colour of the light that the observer notices. Take the speed of light in air as 3x10^8 m/s.
Solution:

f^{'} = f (\frac{c + v_{0}}{c - v_{s}})

= \frac{3 X 10^{8}}{660 X 10^{- 9}} (\frac{3 X 10^{8} + 0}{3 X 10^{8} - 2 X 10^{8}})

= 1, 36 X 10^{15} H z

This corresponds to a wavelength of 220 nm which falls outside the visible spectrum of light and so the observer will see no colour at all.

How can I use the doppler effect equation?

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