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## Main Question or Discussion Point

Consider a spaceship and a source, with no relative motion but spatially separated. At t=0, spaceship moves with velocity [itex]v \hat{a}_x[/itex] w.r.t source and at t = 0 source emits a photon.

After photon has been emitted, the speed of spaceship starts increasing in same direction. So what parameters will change according to the person sitting in spaceship (when the speed is changing).

a) Speed of photon

b) Energy of photon

c) Momentum of photon

I think that all above parameters will remain same.

a) Speed of photon is same in all frames.

b) Tho there is doppler shift which will change the frequency, but it depends only on the instantaneous relative velocity (between source and spaceship) when the photon was being emitted.

c) E = pc, so p should remain same too.

Please correct me if I am wrong. Thanks

After photon has been emitted, the speed of spaceship starts increasing in same direction. So what parameters will change according to the person sitting in spaceship (when the speed is changing).

a) Speed of photon

b) Energy of photon

c) Momentum of photon

I think that all above parameters will remain same.

a) Speed of photon is same in all frames.

b) Tho there is doppler shift which will change the frequency, but it depends only on the instantaneous relative velocity (between source and spaceship) when the photon was being emitted.

c) E = pc, so p should remain same too.

Please correct me if I am wrong. Thanks