An observer is moving in space toward a distant star at 100 km/s while the star is moving toward the observer at 200 km/s;the relative velocity being 300 km/s of approach.What relative change in frequency of the light from the star as seen by the observer? (The speed of light in space is 3.00 ´ 10⁵ km/s).

Question

Quizplus · Accepted Answer

We can use the formula for the Doppler effect on light:
Δf/f = Vr/c
where Δf is the change in frequency, f is the original frequency, Vr is the relative velocity, and c is the speed of light.

Plugging in the values:
Δf/f = 300 km/s / 3.00 × 10^5 km/s
Δf/f = 0.001

So the relative change in frequency is 0.001, which is equivalent to a 0.1% increase in frequency (since the star is moving towards the observer). Therefore, the answer is (C) 0.067% increase.

An Observer Is Moving in Space Toward a Distant Star