Chapter 14

Waves

Waves make up approximately 20 percent of the SAT Physics Subject Test. But
what are they, exactly? Imagine holding the end of a long rope in your hand, with
the other end attached to a wall. Move your hand up and down, and you’ll create a
wave that travels along the rope, from your hand to the wall. This is the basic idea
of a mechanical wave: a disturbance transmitted by a medium from one point to
another, without the medium itself being transported. In the case of water waves,
wind or an earthquake can cause a disturbance in the ocean, and the resulting waves
can travel thousands of miles. No water actually makes that journey; the water is
only the medium that conducts the disturbance.