Section 17.3 Reflec%on —  Occurs when a wave bounces off a surface that it cannot pass through. —  Reflection does not change the speed or frequency of the wave. Refrac%on —  The bending of a wave as it enters a new medium at an angle. —  When a wave enters a new medium at an angle, refraction occurs because one side of the wave moves more slowly than the other side. Diffrac%on —  The bending of a wave as it moves around an obstacle or passes through a narrow opening. Interference —  Occurs when two or more waves overlap and combine together —  There are two types of interference: constructive interference and destructive interference. Construc%ve Interference —  The displacements of waves combine to increase amplitude. Destruc%ve Interference —  The displacements of waves combine to decrease amplitude. Standing Wave —  Is a wave that appears to stay in one place-­‐it does not seem to move through the medium. —  A standing wave forms only if half a wavelength or a multiple of half a wavelength fits exactly into the length of a vibrating cord. True or False —  Reflection occurs when a wave bounces off a surface that it cannot pass through. —  TRUE What happens when a wave reflects off a fixed boundary? —  The reflected wave will turn upside down Why does refrac%on occur when a wave enters a new medium at an angle? —  Refraction occurs because one side of the wave moves more slowly than the other side. True or False —  Refraction always involves a change in speed and direction of a wave. —  TRUE What is required in order for diffrac%on to occur? —  Waves diffract when they encounter an obstacle or pass through a narrow opening. True or False —  A wave diffracts more if its wavelength is small compared to the size of an opening or obstacle. —  FALSE —  A wave diffracts more if its wavelength is LARGE compared to the side of an opening or obstacle. What causes wave interference? —  Wave interference occurs when two or more waves overlap and combine. At certain frequencies, interference between a wave and its reflec%on can produce a(n) —  Standing wave Circle the statement that is true about standing waves. —  A.) A node is a point that has no displacement from the rest position. Give a common example of a standing wave —  The vibrations you can see when plucking a stringed instrument.