If the velocity of an electron in its first orbit of hydrogen atom is `2.1 xx10^(6)` m/s, then its velocity in the third orbit is

Options

A. `18.9xx10^6 m//s`
B. `6.3 xx10^6 m//s`
C. `7xx10^6 m//s`
D. `7xx 10^5 m//s`

Answer

D

Explanation

Orbital velocity `prop 1/n`
`therefore v_3/v_1 = n_1/n_3 = 1/3`
`therefore v_3 = v_1/3 = (2.1xx10^6)/(3) = 7xx10^5 m//s`