A radar gun can determine the speed of a moving automobile by measuring the difference in frequency between emitted and reflected radar waves. What process is used in determining the speed of the car?

Question 7 options:

resonance

refraction

diffraction

doppler effect

Doppler effect.

Explanation:

The velocity of the moving car affects the wavelengths of the reflecting radio waves according to the principle of Doppler effect. Therefore, for a car moving away from the radar gun, the wavelength of the radio waves is increased, and for a car moving towards the gun, the wavelength is decreased. The degree of increase or decreases depends on the speed of the car, so if you know how much a wavelength has changed, you know the velocity of the car.