The quantity $h \nu / K_{B}$ corresponds to

State whether the following statements are true or false:
$(i)$ In Rutherford's atomic model,the Coulombic forces between the nucleus and electrons are mathematically similar to the gravitational forces $F = G \frac{m_1 m_2}{r^2}$.
$(ii)$ Out of every $20000$ $\alpha$-particles,$\sim 10$ particles bounce back after hitting the gold foil.
$(iii)$ In Rutherford's experiment,a zinc sulfide $(ZnS)$ fluorescent screen is placed around the gold foil.
$(iv)$ Rutherford's $\alpha$-particle scattering experiment is related to the size of the atomic nucleus.

What is the angular momentum of an electron when it revolves in orbits?

The wave number of the first line of the Balmer series of $H$ atom is $15200 \ cm^{-1}$. What is the wave number of the first line of the Lyman series of $Li^{2+}$? (in $cm^{-1}$)

Circumference of the first orbit of hydrogen atom is given by the formula :

Two electrons are revolving around a nucleus at distances $r$ and $4r$. The ratio of their time periods is