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

$a$,$b$,$c$,$d$ are electromagnetic radiations. Frequencies of $a$,$b$ are $3 \times 10^{15} \ Hz$,$2 \times 10^{14} \ Hz$,respectively,whereas wavelengths of $c$,$d$ are $400 \ nm$,$750 \ nm$,respectively. The increasing order of their energies is

Explain the properties of electromagnetic waves.

The following sketch represents a specific wave of light. What will be the color of the light represented by this wave?

What is scattering? Which property of electromagnetic radiation can explain it? Explain.

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