If the speed of electron in the Bohr's first orbit of hydrogen atom be x, then the speed of the electron in the third Bohr orbit is

Options

A. `x//9`
B. `x//3`
C. `3x`
D. `9x`

Answer

B

Explanation

Velocity of electron in the nth orbit of hydrogen arom, `v = (2.188 xx 10^(8))/(x) cm s^(-1)`
Velocity in first orbit,
`v_(1) = (2.188 xx 10^(8))/(1) cm s^(-1) = x`
Velocity in third orbit
`v_(3) = (2.188 xx 10^(8))/(x) cm s^(-1) = x//3`