Question

A stationary hydrogen atom emits a photon corresponding to first line of Lyman series. The velocity of recoil of the atom is

• A. 7.29 m/s
• B. 2.79 m/s
• C. 3.2 m/s
• D. 5.32 m/s

Answer 1

The correct option is C 3.2 m/s

$P=\frac{E}{C}=\frac{(13.6-3.4)}{3\times {10}^8}1.6\times {10}^{-19}$
$=\frac{10.2\times 1.6\times {10}^{-19}}{3\times {10}^8}$
$V=\frac{p}{m}=\frac{3.4\times 1.6\times {10}^{-19}}{1.67\times {10}^{-27}\times {10}^8}=V=3.2m{s}^{-1}$