Light of wavelength 659.4 nm is emitted by a star. The wavelength of this light as measured on Earth is 661.1 nm. How fast is the star moving with respect to Earth?
Is it moving toward Earth or away from it?
2007-11-05 04:57:06 · 5 answers · asked by Kelly 1 in Science & Mathematics ➔ Physics
This is a straight-forward Doppler effect question.
Since the light is shifted to longer wavelength that means that the star is moving away from the observer.
delta/L = v/c
where delta=difference in wavelength
L = wavelength at the source
v = relative speed between source and observer
c = speed of light = 3 x 10^8 m/sec
v = delta*c/L
= (661.1 - 659.4 )*3*10^8 / 659.4
= 7.73*10^5 m/sec
2007-11-05 05:20:50 · answer #1 · answered by Charlie149 6 · 0⤊ 0⤋
the star has a red shift ... so it is moving away from earth
Speed and frequency
Derive the relationship Îλ / λ = Îf / f = v / c.
This says that the fractional change in wavelength or frequency is equal to the ratio of the speed of the source to the speed of light.
More at below URL.
2007-11-05 13:16:32 · answer #2 · answered by cpuguy_1 4 · 0⤊ 0⤋
The star is moving away from the earth at a speed of .00258c which is approximately 7.734 x 10 ^5 m/s
2007-11-05 13:07:29 · answer #3 · answered by JJHantsch 4 · 0⤊ 0⤋
Star is moving away - the measured wavelength is longer.
l' = l*(1 -/+v/c) --> l/l' = 1+v/c ---> c*(l'/l -1) = v = -7.71x10^5 m/s
2007-11-05 13:04:39 · answer #4 · answered by nyphdinmd 7 · 1⤊ 0⤋
Moving away.
2007-11-05 13:04:10 · answer #5 · answered by Renaissance Man 5 · 0⤊ 0⤋