Cell membraine i hope that help
Like what our backyards look like
if so then my backyard has tons of flowers and a big white shed
1/2 of a radioactive substance will remain after 3 half lives.
The "medium" is the substance or material that carries a mechanical wave. One of the most important things to remember about waves is that they transport energy, not matter. This makes them different from other phenomenon in physics.
For simple definitions, visit the following website:
https://www.ducksters.com/science/physics/waves.php
