(c) According to Einstein's photoelectric equation, maximum energy of emitted electrons is given by
Kmax=mvmax2=hv−hv0⇒mvmax2=h(v−v0)⋅⋅⋅⋅⋅⋅⋅(i)When, frequency of incident radiation, becomes
2v, then velocity of emitted electron is
v1, hence from Eq. (i), we get
mv12=h(2v−v0)mv12=hv0⋅⋅⋅⋅⋅⋅⋅(ii)Again, when frequency becomes
5v0, the velocity of emitted electron is
v2.
∴ From Eq. (i), we have
mv22=h(5v−v)⇒mv22=4hvDividing Eq. (ii) by Eq. (iii), we get
=⇒()2=()2⇒v1:v2=1:2