The work function for aluminium is $4.125 \mathrm{eV}.$ The cut-off wavelength for photoelectric effect for aluminium is

A beam of monochromatic light of wavelength $\lambda$ ejects photoelectrons from a caesium surface $\left({\mathrm{W}}_0=1.9 \mathrm{eV}\right)$ which are made to collide with hydrogen atoms in ground state. The maximum value of $\lambda$ for which hydrogen atoms may be ionised is

(Take value of $h=6.6\times {10}^{-34}$ in SI units)

A point sources of light is used in a photoelectric effect. If the sources is removed farther from the emitting metal, the stopping potential 

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