Photoelectric emission from a metal begins at a frequency of $6\times {10}^{14} \mathrm{Hz}$. The emitted electrons are fully stopped by a retarding potential of $3.3 \mathrm{V}$.  What will be the wavelength of the incident radiation?

The following graph represents the variation of photo current with anode potential for a metal surface. Here $I_1, I_2$ and $I_3$ represents intensities and ${\gamma }_1,{\gamma }_2,{\gamma }_3$ represents frequency for curves $1, 2$ and $3$ respectively, then

Guess the shape of curve which shows the variation of $v_{\circ }$ with v in case of photoelectric emission shown by the relation where symbols have their usual meaning.

$V_{\circ }=\left(\frac{h}{e}\right)v-\frac{{\varphi }_{\circ }}{e}$

The photoelectric threshold for a certain metal surface is $360 \mathrm{Å}$. If the metal surface is irradiated by a wavelength of $1100 \mathrm{Å}$, the kinetic energy of the emitted photoelectrons is