K1=1.5hv0−ϕ0=0.5hv0
K2=1.5h2v0−hv0=−0.25hv0
∵ Kinetic energy can never be negative so, no emission and i=0
OR
In second case the incident frequency is halved
Incident frequency =21.5v0=0.75v0
Now the incident frequency is less than threshold frequency, so no emission of electron take place therefore no current. (i=0)