Question

Suppose you observe light from a distant galaxy with a diffraction grating and find the angle at which the grating produces maximum intensity corresponding to light emitted by heated sodium. Which of these would show that the galaxy is moving away from the earth?

A. One of the two yellow lines disappears.

B. The two yellow lines are unshifted.

C. The two yellow lines are shifted toward a direction corresponding to a longer wavelength.

D. The two yellow lines are shifted toward a direction corresponding to a shorter wavelength.

Answer 1

I think C since if the galaxy is going away, we observe a decresing of frequency, so an increasing of wavelength

Answer 2

decreasing*

Answer 3

ohh okay!! thank you:)

Answer 4

thanks!! :)