The threshold frequency of a metal is ${\mathrm{v}}_0$. When the light of frequency $2{\mathrm{v}}_0$ is incident on the metal plate, the maximum velocity of the electrons is ${\mathrm{v}}_1$. When the frequency of the incident radiation is increased to $5{\mathrm{v}}_0$, the maximum velocity of the electron emitted is ${\mathrm{v}}_2$. Find the ratio of ${\mathrm{v}}_1$ to ${\mathrm{v}}_2$

For the photoelectric effect in a metal, Figure shows the plot of cut-off voltage versus frequency of incident radiation. Determine the threshold frequency, 

For photoelectric effect in a metal, Fig. $19.14$ shows the plot of cut-off voltage versus frequency of incident radiation. Determine work function of the given metal.