Photon from `n=2` to `n=1` in hydrogen atom is made to fall on a metal surface with work function `1.2eV.` The maximum velocity of photo electron emitted is nearly equal to

Options

A. `6xx10^(5)m//s`
B. `3xx10^(5)m//s`
C. `2xx10^(5)m//s`
D. `18xx10^(5)m//s`

Answer

D

Explanation

` E= E_(2) - E_(1) E_(n) =- (13.6)/(n^2), (1)/(2) mv^2) = E-W`
`(1)/(lambda) = R ((1)/(1^2)-(1)/(alpha^2))` series limit for lyman series
`(1)/(lambda) = R ((1)/(1^2)-(1)/(2^2))` series for lyman first line