Question

Look at the spectrums of a star moving towards Earth and a motionless star.

Which of these is a correct inference that can be draw from the observation of the two spectrums? (2 points)


The spectrum of a motionless star is difficult to be viewed separately using oridinary telescopes.


The spectrum of a motionless star is identical to the spectrum of a star which moves towards Earth.


The spectrum of a star shifts towards the red region when the star moves towards Earth.


The spectrum of a star shifts towards the blue region when the star moves towards Earth.

Answer 1

The answer is; The spectrum of a star shifts towards the blue region when the star moves towards Earth.

This is referred to as the Doppler shift effect. As the star moves closer to the observer, the wavelength of light it produces is ‘compressed’ hence changing its relative frequency (just like the pitch of the siren of an ambulance approaching you).

Answer 2

it is Blue shifted when moving towards Earth