Light radiates from a distant star that is moving towards Earth. In the Earth's frame of reference the light has a wavelength of 400 nm. If the star is moving with a speed of 0.41 c, what wavelength, in nm, will be seen by an observer in the star's frame. Calculated your answer to two decimal places.

Question

Light radiates from a distant star that is moving towards Earth.  In the Earth's frame of reference the light has a wavelength of 400 nm.  If the star is moving with a speed of 0.41 c, what wavelength, in nm, will be seen by an observer in the star's frame.  Calculated your answer to two decimal places.

pixi_dust · Answer

$$\lambda b  = \frac{ \lambda c }{ c + Vb }$$

So (400 * 300,000)/(300,000 + 123,000)
0.41 c = 123,000 kms-1

osprey · Answer

Is this a special relativity question ? http://perendis.webs.com

osprey · Answer

Enclosed is a bit of a guess at a possible solution in pptx. I've based it on the idea that at low speeds the pitch of a sound, say, increases as, say, a train approaches - assuming it's whistling, that is.
Could you let me know if I'm right, please ?

khally92 · Answer

Nope
Sorry but its not correct

Thnk you thou
 when i get the correction I will let you know

irishboy123 · Answer

@osprey

i think you had it until the final jump.

re-do yr reality check, they've given us $\lambda_{observed}$ whch should be smaller than $\lambda_{source} $ as you would measure on the star itself

so we scale it up.

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