The Doppler Effect Flashcards

All 6 cards in this deck

What is the Doppler effect?

The change in observed frequency and wavelength of a wave when the source moves relative to the observer.

What happens to the observed wavelength and frequency when a wave source moves away from an observer?

Observed wavelength increases and observed frequency decreases.

What happens to the observed wavelength and frequency when a wave source moves towards an observer?

Observed wavelength decreases and observed frequency increases.

Why does the siren of an ambulance sound lower in pitch as it drives away from you?

The observed frequency is decreased (wavelength increased) because the source is moving away — the Doppler effect.

True or false? The Doppler effect changes the speed of the waves travelling to the observer.

False. The wave speed stays the same; only the observed wavelength and frequency change.

True or false? The Doppler effect happens for light as well as for sound.

True. Light from a moving source shows a change in observed wavelength and frequency, e.g. red-shift.