Question

Police radar determines the speed of motor vehicles using the same Doppler-shift technique employed for ultrasound in medical diagnostics. Beats are produced by mixing the double Doppler-shifted echo with the original frequency. If 2.25 ✕ 10¹⁰ Hz microwaves are used and a beat frequency of 2,400 Hz is produced, what is the speed (in m/s) of the vehicle? (Assume the same Doppler-shift formulas are valid with the speed of sound replaced by the speed of light.)

Answer 1