Practice Doppler Effect in Physics
Use these practice problems to test your method after reviewing the concept explanation and worked examples.
Quick Recap
The change in observed frequency of a wave that occurs when the source and the observer are moving relative to each other.
An ambulance siren sounds higher-pitched approaching, lower-pitched receding.
Example 1
easyAn ambulance siren emits sound at 700 \text{ Hz}. As the ambulance approaches you at 30 \text{ m/s}, what frequency do you hear? Use v_{\text{sound}} = 340 \text{ m/s}.
Example 2
mediumA train whistle blows at 500 \text{ Hz}. You are stationary and hear 475 \text{ Hz}. Is the train approaching or moving away? What is the train's speed? Use v_{\text{sound}} = 340 \text{ m/s}.
Example 3
mediumA car horn emits 400 \text{ Hz}. You drive toward the stationary car at 20 \text{ m/s}. What frequency do you hear? Use v_{\text{sound}} = 340 \text{ m/s}.
Example 4
hardPolice radar emits microwaves at 10.5 \text{ GHz}. The reflected signal from an approaching car has a frequency shift of 3500 \text{ Hz}. What is the car's speed? Use c = 3 \times 10^8 \text{ m/s} and the Doppler formula \Delta f = \frac{2v_s f}{c} for electromagnetic waves.