Light of wave length 488 nm is produced by an argon laser which is used in the photo electric effect . When light from this spectral line is incident on the cathode , the stopping potential of photo electrons is $0.30\;ev$ . Find the work function of the material from which the cathode is made.given $(h= 6.63 \times 10^{-34}\;Js, me= 9 \times 10^{-31}kg, \; lev =1.6 \times 10^{-19}\;J)$
