The threshold frequency of metal is f₀. When the light of frequency 2f₀ is incident on the metal plate, the maximum velocity of photoelectron is v₁. When the frequency of incident radiation is increased to 5f₀. the maximum velocity of photoelectrons emitted is v₂. The ratio of v₁ to v₂ is ?
a. v₁/v₂ = 1/2
b. v₁/v₂ = 1/8
c. v₁/v₂ = 1/16
d. v₁/v₂ = 1/4