Which of the following radiations are in correct descending order of frequencies?

The power of a source is $4 \, kW$. If it produces $10^{20}$ photons in $1 \, s$,then the radiation emitted from this source belongs to which part of the electromagnetic spectrum?

Write short information regarding electromagnetic waves.

Write the sources of microwaves and infrared waves and their uses.

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.

The ozone layer absorbs