The splitting of spectral lines under the influence of a magnetic field is known as .....

Find the energy of radiation having $7000 \ \mathring{A}$ and $400 \ nm$ wavelength. $\left( h = 6.62 \times 10^{-34} \ J \ s, c = 3 \times 10^8 \ m/s \right)$

Which formula represents the rest mass of an electron?

The work functions $(W_0)$ of $K, Na, Li, Mg$ and $Cu$ are $2.25, 2.30, 2.42, 3.70$ and $4.80 \ eV$ respectively. How many of these metals do not undergo photoelectric effect when a radiation of wavelength $450 \ nm$ is allowed to fall on them? $(1 \ eV = 1.602 \times 10^{-19} \ J)$

What is the wavenumber of a radiation having a wavelength of $0.25 \mu m$?

If the energies of two photons are in the ratio of $3:2$,their wavelengths will be in the ratio of