Tutoring science, the concept of radiation arises. The tutor explains it.

Radiation is electromagnetic energy travelling from its source.

Imagine a radio receiver which you can tune to any frequency. Actual radio station signals will be at the low end, then microwaves, then heat (aka infrared), then visible light. Past visible light is ultraviolet light, then X and gamma rays.

Radiation of higher frequency has higher energy. X and gamma rays have such high energy they can pass through solid objects.

Source:

nasa.gov

symmetrymagazine.org

Jack of Oracle Tutoring by Jack and Diane, Campbell River, BC.