Line spectrum contains information about

The nature of the sun's spectrum is

Consider the following two statements $A$ and $B$ and identify the correct choice in the given answers:
$A :$ Line spectra are due to atoms in the gaseous state.
$B :$ Band spectra are due to molecules.

The collision of an electron with kinetic energy $5.5 eV$ and a hydrogen atom in its ground state can be described as

If the ionisation potential of a helium atom is $24.6 \, V$,the energy required to ionise it will be

An electron of a stationary Hydrogen atom transitions from the fifth energy level to the ground level. The velocity that the atom acquires as a result of photon emission is ( $m=$ mass of the atom,$R=$ Rydberg's constant,$h=$ Planck's constant).