Question

The spectral line for a given element of light received from a distant star is shifted toward longer wavelength side by 0.025%. The velocity of star kin the line of light is:

• A. 7.5×10⁴ m s^-1
• B. -7.5×10⁴ m s^-1
• C. 3.7×10⁴ m s^-1
• D. -3.7×10⁴ m s^-1

Answer 1

Answer: (B)

-7.5×10⁴ m s^-1

Answer 2

: Velocity of star in line of light of

$v = \frac{- \Delta\lambda}{\lambda} \times c = - \frac{0.025}{100} \times 3 \times 10^{8} = - 7.5 \times 10^{4}ms^{- 1}$