U.V. light of wavelenght 800Å & 700Å falls on hydrongen atoms in thir ground state & liberates electrons with kinetic energy 1.8eV and 4eV respectively . Calculate planck 's constant.

Explanation

`E_(1)=(hc)/lambda_(1)-phi_(0) " "E_(2)=(hc)/lambda_(2)-phi_(0) `
`E_(1)-(hc)/lambda_(1)`=`E_(2)-(hc)/lambda_(2)=phi_(0)`
`hc[(1)/lambda_(1)-(1)/lambda_(2)]=E_(1)-E_(2)`
`h=((E_(2)-E_(1))lambda_(1)lambda_(2))/((lambda_(1)-lambda_(2))c)`=`6.57xx10^(-34)`Js