Question

If the shift in the star is towards red end, then:

• A. the star is approaching the earth
• B. the star is receding the earth
• C. the apparent frequency is lesser than actual
• D. the apparent wavelength is lesser than actual

Answer 1

Answer: (B), (C)

The correct options are
B the star is receding the earth
C the apparent frequency is lesser than actual

If the star is moving away from us, its waves are effectively stretched out when they reach Earth, increasing their wavelength. This shifts the star's spectral lines toward the red end of the spectrum. And, The red end of the spectrum has a lower pitch or frequency. Hence, the star is receding the earth and the apparent frequency is lesser than actual.