An electron in a hydrogen atom makes a transition from the $(n+1)^{th}$ orbit to the $n^{th}$ orbit. For large $n$,the wavelength of the emitted radiation is proportional to:

The four lowest energy levels of an $H$-atom are shown in the figure. The number of possible emission lines would be

In an inelastic collision, an electron excites a hydrogen atom from its ground state to an $M$-shell state. $A$ second electron collides instantaneously with the excited hydrogen atom in the $M$-state and ionizes it. At least how much energy must the second electron transfer to the atom in the $M$-state?

The energy required to knock out the electron in the third orbit of a hydrogen atom is equal to

$A$ hydrogen atom absorbs radiation of wavelength $975 \, \text{\AA}$ to transition from the ground state to an excited state. To which energy level will the atom transition?

The minimum energy required by a hydrogen atom in the ground state to emit radiation in the Balmer series is nearly: (in $eV$)