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On a futuristic highway, a 15mlong rocket travels so fast that a red stoplight, with a wavelength of 700nm, appears to the pilot to be a green light with a wavelength of 520nm. What is the length of the rocket to an observer standing at the intersection as the rocket speeds through?

Short Answer

Expert verified

L'=1.449×10-2km→14.49mlength of the rocket to an observer standing at the intersection as the rocket speeds through.

Step by step solution

01

Given Information

We need to find the length of the rocket to an observer standing at the intersection as the rocket speeds through.

02

Simplify 

Consider,

L=15m→1.5×10-2km

λ0=700nm

λ=520nm

First, finding ∆λ,

∆λ=λ-λ0=520nm-700nm=-180nm

Now finding velocity v:

∆λλ0=vc

⇒v=c∆λλ0

v=3×105km/s-180700

v=-7.714×104km/s

Finally, we will find the length of the rocketL'

L'=1-v2c2LL'=1.5×10-21--7.714×10223×1052L'=1.449×10-2km→14.49m

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