Music

Music is nothing but physics and waves. A pluck of the string creates a wave of a specific length that produces a sound of a certain frequency. Air can also create a wave frequency like that of a flute, trumpet, or harmonica. The distinct sound of each instrument is caused by the unique combination of different wave lengths that make up the sound. When plotted on a graph, the sound can be as simple as a sine wave or complex like a heartbeat monitor.
Different harmonics can be created by using the same instrument. In this illustration, the tubing shows how different wave lengths can occur from the same tube.

mirror

I was looking at myself in the mirror when I noticed that I could see my whole body in a mirror that was no more than three feet tall. Why could this occur? I could see my feet because the light rays from my feet reflect off of the mirror at the halfway point between my feet and my eyes. The light from the top of my head reflects off of the mirror where it is halfway between the top of my head and my eyes. By increasing the distance to the mirror, a smaller angle of reflection is required and therefore the mirror can be shorter in length.

CD wave diffraction

So I was driving in my car listening to my CD when I realized that I had been taking waves for granted. Sound waves were being amplified by the speakers and reaching my ears. When I would change the balance and tilt of the car, different speakers changed their amplification in order to make the sound loudest at a specific point in the car. I also realized that a CD works by means of light diffraction. A laser is shown beneath the CD and reflected off of the CD back into a laser reader. The bottom of the CD contains grooves that cause the laser to be deflected back at different lengths. The constructive and destructive interferences allow the CD reader to process the light waves into sound waves.