A beam of light has two wavelengths of $4972\mathrm{Å}$ and $6216\mathrm{Å}$ with a total intensity of $3.6\times {10}^{-3}{\mathrm{Wm}}^{-2}$ equally distributed among the two wavelengths. The beam falls normally on an area of $1{ \mathrm{cm}}^2$ of a clean metallic surface of work function $2.3\mathrm{eV}$. Assume that there is no loss of light by reflection and that each capable photon ejects one electron. The number of photoelectron liberated in $2 \mathrm{s}$ is approximately:

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

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

Given figure shows few data points in a photo-electric effect experiment for a certain metal. The minimum energy for ejection of electrons from its surface is: (Planck's constant $\mathrm{h}=6.62\times {10}^{–34}\text{ J.s}$)

The work function of three photosensitive materials used to build photoelectric devices are given as : Sodium $(2.75 \mathrm{eV}),$ copper $(4.65 \mathrm{eV})$ and gold $(5.1 \mathrm{eV}).$ Which of the following statements is correct. (The frequency of visible light lies in the range $4\times {10}^{14} \mathrm{Hz}$ to $8\times {10}^{14} \mathrm{Hz}) ?$