The electromagnetic waves of frequency $2 \ MHz$ to $30 \ MHz$ are used in:

Given below are some famous numbers associated with electromagnetic radiations in different contexts in physics. State the part of the electromagnetic spectrum to which each belongs.
$(a)$ $21 \; cm$ (wavelength emitted by atomic hydrogen in interstellar space).
$(b)$ $1057 \; MHz$ (frequency of radiation arising from two close energy levels in hydrogen; known as Lamb shift).
$(c)$ $2.7 \; K$ (temperature associated with the isotropic radiation filling all space; thought to be a relic of the 'big-bang' origin of the universe).
$(d)$ $5890 \; \mathring{A} - 5896 \; \mathring{A}$ (double lines of sodium).
$(e)$ $14.4 \; keV$ (energy of a particular transition in $^{57}Fe$ nucleus associated with a famous high-resolution spectroscopic method, Mossbauer spectroscopy).

Which of the following colours of visible light has the lowest energy?

Match List-$I$ with List-$II$:

List-$I$ (Electromagnetic wave)	List-$II$ (Production)
$A$. Microwave	$I$. Electrons in atoms emit light when they move from a higher energy level to a lower energy level
$B$. Visible light	$II$. Radioactive decay of nucleus
$C$. Gamma rays	$III$. Vibration of atoms and molecules
$D$. Infra-red rays	$IV$. Klystron valve or magnetron valve

Choose the correct answer from the options given below:

The correct ascending order of the wavelengths of the following electromagnetic waves is: Ultraviolet,$X$-rays,infrared,gamma rays,and visible light.

Electromagnetic radiation used to sterilise milk is