The frequency order for $\gamma$-rays $(a)$,$X$-rays $(b)$,and $UV$-rays $(c)$ is given as:

Electromagnetic waves with wavelength:
$(i)$ ${\lambda _1}$ is used in satellite communication.
$(ii)$ ${\lambda _2}$ is used to kill germs in water purifiers.
$(iii)$ ${\lambda _3}$ is used to detect leakage of oil in underground pipelines.
$(iv)$ ${\lambda _4}$ is used to improve visibility in runways during fog and mist conditions.
$(a)$ Identify and name the part of the electromagnetic spectrum to which these radiations belong.
$(b)$ Arrange these wavelengths in ascending order of their magnitude.
$(c)$ Write one more application of each.

$A$ charged particle oscillates about its mean equilibrium position with a frequency of $10^9 \ Hz$. The electromagnetic waves produced:

The frequency range from $3 \times 10^9 \, Hz$ to $3 \times 10^{10} \, Hz$ is known as:

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

Which of the following electromagnetic waves has the longest wavelength?