What is an ozone hole?

Cellular phones use radio waves to transmit voice communication in the . . . . . . band.

What is the wavelength range of visible light?

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R.$
Assertion $A:$ $EM$ waves used for optical communication have longer wavelengths than that of microwaves employed in $RADAR$ technology.
Reason $R:$ Infrared $EM$ waves are more energetic than microwaves (used in $RADAR$).
In the light of the given statements,choose the correct answer from the options given below:

Which of the following radiations has the least wavelength?

Which one of the following has the minimum wavelength?