A car with its hooter sounding drives straight towards you. What happens to the sound waves that reach you?
ALonger wavelength, higher pitch
BShorter wavelength, higher pitch
CShorter wavelength, lower pitch
DLonger wavelength, lower pitch
Answer & Solution
Correct answer: B. Shorter wavelength, higher pitch
1. As the car moves towards you it emits each new crest from a position closer to you.
2. The crests on your side of the car are therefore bunched closer together.
3. Crests closer together means a shorter wavelength, and since the wave speed is fixed, a higher frequency.
4. A higher frequency is heard as a higher pitch.
_Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 6: Doppler effect_
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