Choose the correct statements in reference to the photoelectric effect.

(A) There is no time lag between the striking of light and ejection of electrons from the metal surface.

(B) The number of electrons ejected is independent of the intensity of light.

(C) The elements $\mathrm{K}, \mathrm{Rb}$ and Cs can show photoelectric effect when exposed to the beam of light.

The maximum number of orbitals present in $n=4$ energy level of an atom and the maximum number of electrons with spin value $+\frac{1}{2}$ in the same orbitals are respectively

The approximate ratio of the speed of light in vacuum to that of an electron in the first Bohr orbit of hydrogen atom is

If the radius and energy of the second Bohr orbit of hydrogen atom is $r_2$ and $E_2$. respectively. The radius and energy of the third Bohr orbit will be $\_\_\_\_$ respectively.