Question

which of the following electromagnetic waves are not used for communication? a.gamma rays b.microwaves c.infrared waves d.radio waves

Answer 1

Gamma rays are not used for communication.

-- We have no safe way to generate them.
-- We have no cheap way to detect them.
-- We have no way to impress information on them (modulate them).
-- They're dangerous.

Otherwise they're ideal for communication.