The maximum kinetic energy of the photoelectrons is found to be 6.63×10−19 J, when the metal is irradiated with a radiation of frequency2×1015 Hz The threshold frequency of the metal is about
K.E=h(v−vo)
vo=v−K.Eh
=2×1015−6.63×10−196.63×10−34
=1×1015 s−1