Photoelectrons of threshold wavelength350 nm are emited by u.v light of 250 nm wavelength, from a metal surface. Calculate the kinetic energy of the emitted electrons.

Explanation

i). `KE=hv-W_(0)=(hc)/(lambda)-(hc)/(lambda_(0)) = hc ((1)/(lambda)-(1)/(lambda_(0)))=(6.626xx10^(-34)Js xx 3.0 xx 10^(8) ms^(-1))/(10^(-9)m) ((1)/(250)-(1)/(350))`
`=(6.626 xx 10^(-34)Js xx 3.0 xx 10^(8)ms^(-1))/(10^(-9)m) xx 1.143 xx 10^(-3) =2.272 xx 10^(-19)J`