Using Einstein's photoelectric equation,
E=W0+Kmax
when light of frequency,2v0 is incident on a meal plate,
h(2v0)=hv0+12mv12
hv0=12mv12---------------(1)
when light of frequency,5v0 is incident on a metal plate
h(5v0)=hv0+12mv22
hv0=12mv22----------------(2)
Dividing equation (1) and (2)
14=√21√22
∴v1v2=12
Hence,
option (A) is correct answer.