Question

The wavelength of $H$${}_{\alpha }$ line in hydrogen spectrum was found to be $6563$ $\stackrel{o}{A}$ in the laboratory. If the wavelength of same line in the spectrum of a milky way is observed to be $6568$ $\stackrel{o}{A}$, then recession velocity of milky way will be

• A. $105$ m/s
• B. $1.05\times {10}^6$ m/s
• C. $10.5\times {10}^6$ m/s
• D. $0.105\times {10}^6$ m/s

Answer 1

The correct option is B $1.05\times {10}^6$ m/s

$\nu =\frac{△\lambda }{\lambda }\times c$

$=\frac{6586-6263}{6563}\times 3\times {10}^8$

$=1.05$ $\times$ 10${}^{6}m/s$