When a beam of 10.6 eV photons of intensity $2.0 \mathrm{~W} / \mathrm{m}^2$ falls on a platinum surface of area $1.0 \times 10^{-4} \mathrm{~m}^2$ and work function $5.6 \mathrm{eV} .0 .53 \%$ of the incident photons eject photoelectrons. The number of photoelectrons emitted per second is

A metal surface is illuminated with photons of energies $E_1=4 \mathrm{eV}$ and $E_2=2.5 \mathrm{eV}$ respectively. The ratio of maximum speeds of the photoelectrons in two cases is 2 . Work function of metal surface will be

When $${ }_{92} \mathrm{U}^{235}$$ undergoes fission, $$0.1 \%$$ of its original mass is changed into energy. How much energy is released if $$5 \mathrm{Kg}$$ of $${ }_{92} \mathrm{U}^{235}$$ undergoes fission?

The de-Broglie wavelength of a proton $$\left(m=1.67 \times 10^{-27} \mathrm{~kg}\right)$$ acclerated through a potential difference of $$2 \mathrm{~kV}$$ is