Threshold wavelength of a metal is 230 nm. What will be the kinetic energy of photoelectrons ejected when the metal is irradiated with wavelength 180 nm? `(h = 6.626 xx 10^(-34)Jsec)`

Explanation

Absorbed energy from light = Threshold energy + kinetic energy of photoelectrons
`(hc)/(lambda) = (hc)/(lambda_(0)) + K. E rArr K. = hc [ (1)/(lambda) - (1)/(lambda_(0))]`
`=6.262 xx 10^(-34) xx 3 xx 10^(8) xx [ (1)/(180 xx 10^(-9) ) - (1)/(230 x 10^(-9)]`
`=6.626 xx 10^(-34) xx 3 xx 10^(8) xx 10^(9) [ (1)/(180) - (1)/(230)]`
`1.9878 xx 10^(-16) [ 5. 55 xx 10^(-3) - 4.347 xx 10^(-3)]`
`2.4 xx 10^(-19) J`