contestada

An observer is moving in space toward a distant star at 200 km/s while the star is moving toward the observer at 400 km/s; the relative velocity being 600 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).

Respuesta :

IsrarAwan
The correct answer is: 0.2% (decrease)

Explanation:

The observed frequency can be found by using the following equation:
[tex]v = v_o ( \frac{1 + \frac{v_{observer}}{c}}{1- \frac{V}{c}} )[/tex] --- (1)

Where [tex] v_{observer} [/tex] = Speed of the observer = 200 *1000 m/s
V = speed of the star = 400 *1000 m/s

Plug in the values in (1):
(1) => [tex]v = v_o ( \frac{1 + \frac{200*10^3}{3*10^8}}{1- \frac{400*10^3}{3*10^8}} )[/tex]

[tex]v = v_o ( 1.002 )[/tex] --- (2)

Change in frequency is given as: [tex] \frac{v_o - v}{v_o} * 100[/tex]% --- (3)

Put (2) in (3):
[tex]\frac{v_o - 1.002*v_o}{v_o} * 100[/tex]%

=> -0.2%

Negative sign shows that it decreases!

Hence it is 0.2% (decrease).






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