$A$ stationary hydrogen atom emits a photon corresponding to the first line of the Lyman series. The recoil velocity of the atom is nearly (in $m/s$)

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

The solar spectrum is an example of

Match the following:

$1$. Burning candle	$i$. Line spectrum
$2$. Sodium vapour	$ii$. Continuous spectrum
$3$. Bunsen flame	$iii$. Band spectrum
$4$. Dark lines in solar spectrum	$iv$. Absorption spectrum

An electron of a stationary hydrogen atom passes from the fifth energy level to the ground level. The velocity that the atom acquired as a result of photon emission will be

Highly excited states for hydrogen-like atoms (also called Rydberg states) with nuclear charge $Ze$ are defined by their principal quantum number $n$,where $n \gg 1$. Which of the following statement$(s)$ is(are) true?
$(A)$ Relative change in the radii of two consecutive orbitals does not depend on $Z$
$(B)$ Relative change in the radii of two consecutive orbitals varies as $1/n$
$(C)$ Relative change in the energy of two consecutive orbitals varies as $1/n^3$
$(D)$ Relative change in the angular momenta of two consecutive orbitals varies as $1/n$