The threshold frequency of a metal is \( f_0 \). When the light of frequency \( 2 f_0 \) is incident on the metal plate, the maximum velocity of photoelectrons is \( v_1 \). When the frequency of incident radiation is increased to \( 5 f_0 \), the maximum velocity of photoelectrons emitted is \( v_2 \). The ratio of \( v_1 \) and \( v_2 \) is:
