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),1/2mv^(2)=E-W`
`R(1/(l^(2))-l/2^(2))` series for lyman first line
`1/lambda=R(1/l^(2)-1/2^(2))` series for lyman first `"line" `