The work function for a metal whose threshold wavelength is $5000 \stackrel{\circ }{\mathrm{A}}$ is

Assertion: If the maximum kinetic energy of electrons emitted by a photocell is $5 \mathrm{eV}$, then the stopping potential is $5 \mathrm{V}$.

Reason: Stopping potential for the fastest photoelectrons is numerically equal to their kinetic energy.

The work function of metals is in the range of $2 \mathrm{eV}$ to $5 \mathrm{eV}$. Find which of the following wavelength of light cannot be used for the photoelectric effect. (Consider, $\mathrm{Planck} \mathrm{constant}=4\times {10}^{-15}\mathrm{eVs},$   $\mathrm{velocity} \mathrm{of} \mathrm{light} =\left.3\times {10}^8\mathrm{m} {\mathrm{s}}^{-1}\right)$