Ionisation energy of $Li$ (Lithium) atom in ground state is $5.4 \ eV$. Binding energy of an electron in $Li^+$ ion in ground state is $75.6 \ eV$. Energy required to remove all three electrons of Lithium $(Li)$ atom is ........... $eV$.

$A$ 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.

The solar spectrum is an example of

Band spectrum is obtained when the source emitting light is in the form of

The splitting of a spectral line into groups under the effect of an electric or magnetic field is called:

Which of the following elements was discovered by the study of Fraunhofer lines?