How are infrared waves produced?

To which region of the electromagnetic spectrum does the frequency $1\, GHz$ correspond?

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:

If the frequencies of $X$-rays,$\gamma$-rays,and ultraviolet rays are $a, b$,and $c$ respectively,then which of the following is correct?

If wavelengths of visible rays, microwaves, and $X$-rays are $\lambda_v$, $\lambda_m$, and $\lambda_x$ respectively, then which of the following relations is correct?

The frequency range of visible light is . . . . . . .