Question

The wavelength of spectral line coming from a distance star shifts from 600 nm to 600.1nm. The velocity of the star relative to earth is:

• A. $50kms^{- 1}$
• B. $100kms^{- 1}$
• C. $25kms^{- 1}$
• D. $200kms^{- 1}$

Answer 1

Answer: (A)

$50kms^{- 1}$

Answer 2

: Here $\lambda = 600nm$

$\Delta\lambda = 600.1nm - 600nm = 0.1nm$

As $\frac{V_{s}}{c} = \frac{\Delta\lambda}{\lambda}$

}{= 50 \times 10^{3}ms^{- 1} = 50kms^{- 1}}$$