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Physics Problem

A helium-neon laswer produces light with a peak wavelength of 633 nm when at rest. Imagine that such a laser is being carried on a spaceship. If you observe light from the spaceship's laser to have a wavelength of 610 nm, at least how fast is the spaceship moving? Is it moving toward you or away?

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Arturo O. | Experienced Physics Teacher for Physics TutoringExperienced Physics Teacher for Physics ...
5.0 5.0 (66 lesson ratings) (66)
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This is a Doppler shift problem.  Shorter wavelength means you have a blue shift, so the source is moving toward the observer.  Use the relation
 
Δλ/λ0 = v/c
 
v = c(Δλ/λ0)
 
c = speed of light = 3 x 108 m/s
 
Δλ = (633 - 610) x 10-9 m = ? m
 
λ0 = 633 x 10-9 m
 
Plug in the numbers and get v in m/s.

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