Supposing the electron of the $H$ atom is present in the $L$ shell. If it liberates $10.2 \ eV$,what is the energy of the system? ............. $eV$

Based on equation $E = -2.178 \times 10^{-18} \ J \ \frac{Z^2}{n^2}$,certain conclusions are written. Which of them is not correct?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$:
Assertion $A$: In the photoelectric effect,the electrons are ejected from the metal surface as soon as the beam of light of frequency greater than threshold frequency strikes the surface.
Reason $R$: When the photon of any energy strikes an electron in the atom,transfer of energy from the photon to the electron takes place.
In the light of the above statements,choose the most appropriate answer from the options given below:

What is the radius ratio for the $2^{nd}$ orbit of $Li^{+2}$ ion to the $3^{rd}$ orbit of $Be^{+3}$ ion?

In Rutherford's experiment,generally the thin foil of heavy atoms,like gold,platinum etc. have been used to be bombarded by the $\alpha$-particles. If the thin foil of light atoms like Aluminium etc. is used,what difference would be observed from the above results?

What is the ratio of the radius of the second Bohr orbit to the first Bohr orbit of the $H$ atom?