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

The work functions of two metals $\left(\mathrm{M}_{\mathrm{A}}\right.$ and $\left.\mathrm{M}_{\mathrm{B}}\right)$ are in the $1: 2$ ratio. When these metals are exposed to photons of energy 6 eV , the kinetic energy of liberated electrons of $M_A: M_B$ is in the ratio of $2.642: 1$. The work functions (in eV ) of $M_A$ and $M_B$ are respectively.