Question

One astronomer has observed an apparent lengthening of the electromagnetic waves given off by a star. Which of these conclusions is correct about the star?Its parallax is increasing. It is moving towards Earth. Its wavelength is decreasing. It is moving away from Earth.

Answer 1

I think the correct answer from the choices listed above is the last option. The conclusion about the star would be that it is moving away from  Earth. Lengthening of the waves means that wavelength getting larger this occurs when a body giving off light is moving away. Hope this answers the question.

Answer 2

Answer:

It is moving away from Earth.

Explanation:

The electromagnetic waves given off by a star is bring observed by an astronomer. The waves seem to be lengthening. This means the apparent wavelength of the waves is increasing. It can be explained from Doppler's effect. Doppler's effect states that there is change in apparent wavelength of light when there is relative motion between the source and the observer.

The apparent wavelength decreases when the source and observer approach each other while it increases when they are moving apart.

In the given situation, since the apparent wavelength is increasing, it means the star is moving away from the Earth and we are observing a red shift.