......................say a photon is leaving a star which is moving away from us, by the doppler effect the photon will be red shifted, hence it's wavelength has incresed. But the energy of a photon is given by E=hc/wavelength, where h is planks constant and c the speed of light. so if you were to measure the energy the photon had when leaving the star
(you being stationary with respect to the star) compaired to it reaching earth it would have lost energy just because the star was moving away? what happend to this energy or is it just a relitive thing? any comments welcome. Thanks.
2007-07-11 03:09:23 · 7 answers · asked by s 2 in Science & Mathematics ➔ Physics
I think it's just relative. The doppler effect is all about relative movement. The question words it strangely and says that the wavelength will be increased. An increase in wavelength means a decrease in frequency and a lower energy.
This shift is what make it apper that the photon has lost energy but really it just looks that way to us.
2007-07-11 03:16:09 · answer #1 · answered by Gwenilynd 4 · 1⤊ 0⤋
This is not an illusion.
In your reference frame the photon was never a blue one. It was always a red one. It was red when it was emitted and red when it arrived.
Only in the rest frame of the star was it blue - and you are not in that rest frame.
Energy is - like so much else - relative.
2007-07-11 15:33:34 · answer #2 · answered by Anonymous · 0⤊ 0⤋
You comparing the photon's energy from two different reference points. Relativity is in essence, relative to your 'frame of reference'.
It been a long time since i did physics, so i may have misinterpreted your point
2007-07-11 15:51:51 · answer #3 · answered by Anonymous · 0⤊ 0⤋
If you are stationary relative to the star, there would not be any red-shifting. In fact your question contradicts itself, "a star which is moving away from us" and "you being stationary relative to the star"
2007-07-14 16:03:15 · answer #4 · answered by Anonymous · 0⤊ 0⤋
Motion of am emitter of light has no effect o9n the speed of light, the photon leaves at the full speed of light with no acceleration time and it retains this speed until it is stopped.
2007-07-14 12:50:33 · answer #5 · answered by johnandeileen2000 7 · 0⤊ 0⤋
You answered yourself in your last line. It's relative to the observed frequecy...the source frequency has not changed..it's merely an illusion relative to the observer.
The speed of C is constant, and does not change regardless.
When you say it will have lost energy ....that is simply not true. You can't "lose" energy, you can only change it.
physics is truly mind boggling isn't it ?
2007-07-11 10:32:19 · answer #6 · answered by Anonymous · 0⤊ 0⤋
This website might help you.
http://en.wikipedia.org/wiki/Redshift#Doppler_effect
2007-07-11 11:04:34 · answer #7 · answered by Black 7 · 0⤊ 0⤋