Electromagnetic radiation of wavelength 663 nm is just sufficient to ionise the atom of metal A. The ionization enegy of metal A in kJ mol^$$-$$1 is __________. (Rounded off to the nearest integer)

[h = 6.63 $$\times$$ 10^$$-$$34 Js, c = 3.00 $$\times$$ 10⁸ ms^$$-$$1, N_A = 6.02 $$\times$$ 10²³ mol^$$-$$1]

Among the following, number of metal/s which can be used as electrodes in the photoelectric cell is _________. (Integer answer)

(A) Li

(B) Na

(C) Rb

(D) Cs

A proton and a Li³⁺ nucleus are accelerated by the same potential. If $$\lambda _{Li}$$ and $$\lambda _p$$ denote the de Broglie wavelengths of Li³⁺ and proton respectively, then the value of $${{{\lambda _{Li}}} \over {{\lambda _p}}}$$ is x $$ \times $$ 10^-1.
The value of x is ______. (Rounded off to the nearest integer)
[Mass of Li³⁺ = 8.3 mass of proton]

The work function of sodium metal is 4.41 $$ \times $$ 10^–19 J. If photons of wavelength 300 nm are incident on the metal, the kinetic energy of the ejected electrons will be (h = 6.63 $$ \times $$ 10^–34 J s; c = 3 $$ \times $$ 10⁸ m/s) ________ × 10^–21 J.