Physics Waves MDCAT 2009
PMDC Verified Question 122 of 125
What is it that we use to calculate the speeds of distant stars and galaxies?
A
Doppler Effect
B
Beats
C
Interference
D
All of the above
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: Doppler Effect
Concept:

The Doppler Effect is the apparent change in the frequency or wavelength of a wave due to the relative motion between the source and the observer.

Solution:

  • When stars or galaxies move away from Earth, the light they emit gets stretched, shifting towards the red end of the spectrum (Redshift).


  • By measuring this exact shift in spectral lines, astronomers use the Doppler formula for light to precisely calculate the radial speed of these distant celestial bodies.


Why other options are incorrect:

Beats (acoustic amplitude modulation) and interference (superposition of waves) do not inherently provide relative velocity data for distant astrophysical objects.

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