Question

The wavelength of light received from milky way is 0.4% higher than that from the same source on earth. The velocity of milky way with respect to earth will be

• A. $0.2\times {10}^{6}m{s}^{-1}$
• B. $1.2\times {10}^{6}m{s}^{-1}$
• C. $2\times {10}^{6}m{s}^{-1}$
• D. $5\times {10}^{6}m{s}^{-1}$

Answer 1

The correct option is B $1.2\times {10}^{6}m{s}^{-1}$

$\Delta \lambda =\frac{v}{c}\lambda$

$v=\frac{\Delta \lambda }{\lambda }c$

$v=(\frac{\Delta \lambda }{\lambda }\times 100)\times \left(\frac{c}{100}\right)=0.4\times \left(\frac{3.0\times {10}^8}{100}\right)=1.2\times {10}^{6}m{s}^{-1}$