Which emission transition series is obtained when an electron jumps from $n_2 = \infty$ to $n_1 = 1$?

Splitting of spectral lines when atoms are subjected to a strong electric field is called:

Wavenumber for a radiation having $5800 \ \mathring{A}$ wavelength is $x \times 10 \ cm^{-1}$. The value of $x$ is . . . . . . . .

What is interference in the context of electromagnetic radiation?

Work function $(W_0)$ values of six metals (in $eV$) are given below: $Li: 2.42, Mg: 3.7, Cu: 4.8, Ag: 4.3, K: 2.25, Na: 2.3$. How many of the above metals do not eject the electrons when they are made to strike with radiation of wavelength $400 \text{ nm}$? $(h = 6.62 \times 10^{-34} \text{ Js})$

Which one of the following frequencies of radiation (in $Hz$) has a wavelength of $600 \ nm$?