This is a writing exercise for the student, and answers will vary.
Work Step by Step
Sample: Hey Grandma! I'm learning about waves, which are vibrations that travel in a medium. An example would be water waves rippling across a pond, or traveling waves in an oscillating clothesline. It turns out that when two waves arrive at the same place at the same time, they can reinforce each other (if both waves wanted to push the medium in the same direction, their combined effect is larger), or even cancel each other (if they want to push the medium in opposite directions). An application of this is in those noise-canceling headphones that you use on the plane. A small microphone on the outside of the earcups detects sound waves that are about to hit your ears. The electronics almost instantaneously play an "upside-down" version of that sound that arrives at your ear at the same time that the original sound does. The "superposition" of the two waves results in an eerie quiet.