The Doppler Effect describes the change in frequency of a wave (usually sound or light) perceived by an observer moving relative to the source of the wave. If the source and observer are moving toward each other, the perceived frequency increases (higher pitch for sound, blueshift for light). Conversely, if they're moving apart, the perceived frequency decreases (lower pitch for sound, redshift for light). The effect's magnitude depends on the relative velocities of the source and the observer.
The formulas used to describe the Doppler effect differ slightly depending on whether it's the source or the observer that's moving, and whether the wave is sound or light. For sound, we consider the speed of sound in the medium. For light, we use the principle that the speed of light is constant for all observers.
Match each term with its definition:
| Term | Definition |
|---|---|
| 1. Doppler Shift | a. The speed of the wave in the medium. |
| 2. Frequency | b. The change in frequency due to relative motion. |
| 3. Wavelength | c. The distance between successive crests of a wave. |
| 4. Velocity | d. The rate at which a wave repeats itself. |
| 5. Medium | e. The speed and direction of an object's movement. |
(Match the correct letters with the numbers!)
The Doppler Effect occurs when there is relative ______ between a wave source and an ______. If the source is moving toward the observer, the observed frequency is ______ than the source frequency. This phenomenon is used in many applications, including ______ guns and medical ______.
(Word Bank: motion, higher, observer, radar, imaging)
Explain how the Doppler Effect is used in astronomy to determine whether a star is moving towards or away from Earth.
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