In the spectrum of hydrogen atom, the ratio of the longest wavelength in Lyman series to the longest wavelength in the Balmer series is

In gold foil experiment number of deflected $\alpha -$ particles at angle $90^o$ is $63$ than number of $\alpha -$ particle deflected at $120^o$ is

The number of completely filled shells for the element ${ }_{16} S ^{32}$ is

Hydrogen $(H)$, deuterium $(D)$, singly ionized helium $(H{e^ + })$ and doubly ionized lithium $(Li)$ all have one electron around the nucleus. Consider $n =2$ to $n = 1 $ transition. The wavelengths of emitted radiations are ${\lambda _1},\;{\lambda _2},\;{\lambda _3}$ and ${\lambda _4}$ respectively. Then approximately

The Rutherford $\alpha$-particle experiment shows that most of the $\alpha$-particles pass through almost unscattered while some are scattered through large angles. What information does it give about the structure of the atom