doppler shift
Học thuậtThân thiện
Definition
- Noun:
- The change in the observed frequency of a wave (such as sound or light) when there is relative motion between the source of the wave and the observer. This effect causes the frequency to increase (a shift toward higher frequencies/bluer light) when the source and observer are moving closer together, and to decrease (a shift toward lower frequencies/redder light) when they are moving apart.
Usage Examples
- Noun:
- Astronomers use the Doppler shift of light from distant stars to measure their speed and direction.
- The change in pitch of a passing siren is a common example of the Doppler shift in sound waves.
Advanced Usage
"Redshift": A specific type of Doppler shift where the observed frequency of light decreases (shifts toward the red end of the spectrum), indicating the source is moving away from the observer. This is a key piece of evidence for the expansion of the universe.
- The redshift of galaxies tells us the universe is expanding.
"Blueshift": A specific type of Doppler shift where the observed frequency of light increases (shifts toward the blue end of the spectrum), indicating the source is moving toward the observer.
- The blueshift observed in the star's spectrum indicates it is moving toward our solar system.
Variants and Related Words
- Doppler effect (n): The broader phenomenon of which the Doppler shift is a quantitative measure. It describes the (relative motion) and the (change in frequency).
- The Doppler effect explains why a train's horn sounds different as it passes by.
Synonyms
- Frequency shift: A more general term for a change in wave frequency, which can be caused by the Doppler effect or other phenomena.
Related Phrases
- "To exhibit a Doppler shift": To show a measurable change in frequency due to relative motion.
- The spectral lines from the star exhibit a significant Doppler shift.
Noun
- change in the apparent frequency of a wave as observer and source move toward or away from each other