Question

How is electromagnetic energy measured?

Answer 1

Radio, microwave, infrared, visible telescopes are all used.

Explanation:

Electromagnetic waves are a very broad spectrum. The devices used to measure them are designed to respond in some way to their presence (detection). These are usually various forms of antennae for radio and microwaves, and optics/CCD for infrared and visible light.

See the following pages for more information:
http://www.pion.cz/en/article/electromagnetic-spectrum