Question

If an electrons jumps from `m^(th)` orbit to the nth orbit `(mgtn)` the energy of the atom changes from `E_(m)` . This extra energy `E_(m)-E_(n)` is emitted as a photon whose wavelength is given by `1/lambda=RZ^(2)(1/n^(2)-1/m^(2))` Where `R=1.09xx10^(7)m^(-1)` (Rydberg constant) A photon ejected from the transition of electron from m^(th) excited state of `He^(+)` ion to `n^(th)` state is allowed to fall on a photoelectric material with work function,`phi=7eV`. [Given `h=4.14xx10^(-15)eVs` and `c=3xx10^(8)ms_(1)]`
The photo -electric effect will take place for the transition of electron from
A. `3^(rd)` orbit to `2^(nd)`
B. `4^(th)` orbit to `3^(rd)` orbit
C. `5^(th)` orbit to `3^(rd)` orbit
D. Photoelectron can not ejected

Answer 1

Correct Answer - A
`therefore1/lambda=1.09xx10^(7)xx4(1/4-1/3) Rightarrow lambda=165nm`
` Rightarrow phi =7eV=(hc)/lambda_(0)=(hc)/phi=177nm`
` therefore lambda lt lambda_(0)` Photoelectric effect will occure