Fill in the Blanks 1 - Waves and SoundOnline version Chapter 12, Lesson 1: "Waves and Sound". Use your textbook to help you fill in the blanks pages 644 - 655. Click the word. by Naneth Burquez 1 Compression Frequency Wavelength Period effect Rarefaction Refraction Reflection Doppler Amplitude 1 . - : when the direction of a wave changes because of a change in medium . 2 . - : a measure of how many waves crests or troughs pass a given point in one unit of time . 3 . - : when the pitch of a sound changes because the source of the listener is in motion . 4 . - : the amount of time it takes for a wave to complete one full circle . 5 . - : the distance between wave crests or troughs . 6 . - : an area in a sound wave where particles of matter are spread apart . 7 . - : an area in a sound wave where particles of matter are pushed together . 8 . - : the height of a wave from its trough or crest to its midpoint , which is also a measure of the wave's intensity . 9 . - : how waves bounce off an object and change their direction of travel .