Physics Waves PMDC 2020
PMDC Verified Question 92 of 125
Astronomers calculate speed of distant stars and galaxies using which of the following phenomena?
A
Beats
B
Interference
C
Superposition principle
D
Doppler effect
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Doppler effect
Concept:

The Doppler Effect applies to electromagnetic waves (like starlight) just as it does to sound.

Solution:

  • When stars or galaxies are moving relative to Earth, the spectral lines of the light they emit get shifted.


  • If a galaxy moves away, the light stretches into longer wavelengths (Redshift). If it approaches, it compresses (Blueshift).


  • By quantifying this shift using Doppler formulas, astronomers accurately deduce the radial velocity (speed) of these distant celestial bodies.


Why other options are incorrect:

Beats, interference, and superposition describe wave interactions, not velocity-induced frequency shifts.

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