Question #12 is D and Question #1 is D A spectral line of a star is observed to
ID: 2035989 • Letter: Q
Question
Question #12 is D and Question #1 is D
A spectral line of a star is observed to change from 600nm in the lab to 480nm.The star is A. moving awayfrom us at speed (1/9)c B. moving towards us at speed (1/9)c C. moving away from us at speed (9/41)c Q12. D. moving towards us atspeed (9/41)c E. none of the above A railway platform has a proper length of 200m.A superfast train(nicknamed the flying Scotsman) flys past the station, not stopping, and covers the distance ofthe platform in 0.5 us according to someone on the train. What is the speed of the train relative a stationary observer on the platform? Q1. A. 0.5c B. 0.65c C. 0.75c D. 0.8c E. 0.99cExplanation / Answer
Q12. As per Doppler Red shift equation, the velocity of star is
V = C [1 - Shifted wavelength/observed wavelength]
= C[1-480/600]
= C[1 - 4/5]
= C[1/5]
So the Answer is none of the above. Option (E)
Q1. The Distance of the platform is 200m.
Time taken by the train to cross the platform is 0.5 micro seconds.
The velocity equation is V = Distance / Time
V = (200 / 0.5) * 1000000 = 400000000 m /s.
By converting this into Speed of light in vacuum ( c = 300000 km/s)
We will get 1.35 spped of light in vacuum.
So from the options...Option (A) matches approximately which is 0.5C