key term - Doppler shift

Definition

Doppler shift is the change in frequency or wavelength of a wave in relation to an observer moving relative to the source of the wave. It is commonly observed with sound waves, such as when a vehicle sounding a siren approaches and then recedes from an observer.

5 Must Know Facts For Your Next Test

1. The Doppler shift causes the frequency of a sound wave to increase as the source approaches the observer and decrease as it moves away.
2. The amount of shift depends on the relative speed between the source and observer.
3. For sound waves, if both source and observer are moving towards each other, their speeds are additive in calculating the shift.
4. The formula for calculating Doppler shift for sound is $f' = f \frac{v + v_0}{v - v_s}$ where $f'$ is observed frequency, $f$ is emitted frequency, $v$ is the speed of sound, $v_0$ is the velocity of observer, and $v_s$ is velocity of source.
5. Doppler shifts are also applicable to electromagnetic waves like light, leading to redshift (moving away) and blueshift (approaching).

Review Questions

Related terms

Doppler Effect:

The overall phenomenon where observed frequency changes due to relative motion between a source and an observer.

Redshift:

A phenomenon where light or other electromagnetic radiation from an object increases in wavelength (or shifts to red) as it moves away from an observer.

Blueshift: A phenomenon where light or other electromagnetic radiation decreases in wavelength (or shifts to blue) as it moves towards an observer.