The correct representation of the wavelength-intensity relationship of an ideal black body radiation at two different temperatures $T_{1}$ and $T_{2}$ (where $T_{2} > T_{1}$) is:

Maximum number of spectral lines possible when an electron jumps from $5^{th}$ excited state to ground state in a sample containing only one Hydrogen atom will be

Why does the spectrum of an atom contain many lines even if only one electron is excited?

The wavenumber of the first line $(n_2=3)$ in the Balmer series of hydrogen is $\bar{\nu}_1 \ cm^{-1}$. What is the wavenumber (in $cm^{-1}$) of the second line $(n_2=4)$ in the Balmer series of $He^{+}$?

Calculate the energy of half a mole of photons of a radiation with a frequency of $3 \times 10^{12} \ Hz$.

The ionisation potential of a hydrogen atom is $-13.6 \ eV$. What will be the energy of the atom corresponding to $n = 2$?