The wavelength of photon 'A' is 400 nm. The frequency of photon 'B' is $10^{16} \ \text{s}^{-1}$. The wave number of photon 'C' is $10^4 \ \text{cm}^{-1}$. The correct order of energy of these photons is :

The wave numbers of three spectral lines of H atom are considered. Identify the set of spectral lines belonging to Balmer series.

( $\mathrm{R}=$ Rydberg constant)

Figure 1. electron probability density for 2 s orbital

Figure 2. wave function for 2s orbital

Which of the following point in Figure 2 most accurately represents the nodal surface as shown in Figure 1?

The wavelength of spectral line obtained in the spectrum of $\mathrm{Li}^{2+}$ ion, when the transition takes place between two levels whose sum is 4 and difference is 2 , is