The spin quantum numbers $+1/2$ and $-1/2$ indicate that...

The spectrum obtained from a sodium vapour lamp is an example of

The energy required to remove one electron from a helium atom is $24.6 \, eV$. What is the energy required to remove both electrons from the helium atom (in $, eV$)?

The ionisation energy of an electron in the ground state of a helium atom is $24.6 eV$. The energy required to remove both electrons is: (in $eV$)

$A$ beam of ultraviolet light of all wavelengths passes through hydrogen gas at room temperature,in the $x-$ direction. Assume that all photons emitted due to electron transition inside the gas emerge in the $y-$ direction. Let $A$ and $B$ denote the lights emerging from the gas in the $x$ and $y$ directions respectively.

In a $He-Ne$ laser,the metastable state exists in: