Behavior of Waves
Reflection, Refraction, Diffraction and
Interference in waves
Reflection
• Reflection occurs when a wave bounces off of
a surface it cannot pass through
• It is like when a ball hits a wall and bounces
back
• Reflection does not change the speed or
frequency of a wave
• the wave can be flipped upside down if the
boundary is fixed
Refraction
• Refraction is 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
• Refraction occurs only when the two sides of a
wave travel at different speeds
Diffraction
• Diffraction is the bending of a wave as it
moves around an obstacle or passes through a
narrow opening
• If the wavelength is small compared to the
opening then the diffraction will be little
• The larger the wavelength compared to the
obstacle or opening, the larger the diffraction
Interference
• Interference occurs when two or more waves
overlap and combine together
• The two types of interference are constructive
interference and destructive interference
• Waves increase in amplitude in constructive
interference and decrease in amplitude in
destructive interference
Constructive Interference
• Constructive interference occurs when two or
more waves combine to produce a wave with
a larger displacement
• If two transverse waves meet then the crest
will be higher and the trough will be lower
according to the amplitude of the two waves
Destructive Interference
• Destructive interference occurs when two or
more waves combine to produce a wave with
smaller displacements
• Destructive interference of transverse waves
will produce a wave with a smaller crest and
trough according to the size of the waves
meeting each other
Standing Waves
• A standing wave is a wave that appears to stay
in one place, it does not seem to go through a
medium
• This can be seen if you tie a rope to a chair
and shake the other end of the rope, at some
point the incoming waves will meet the
reflected waves
Nodes and Antinodes
• A node is a point on a standing wave that has
no displacement from the rest position
• At the node there is complete destructive
interference between the incoming and
reflected waves
• An antinode is a point where a crest or trough
occurs midway between two nodes
Standing Waves
• 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
• Once you find the frequency that produces a
standing wave, doubling or tripling the
frequency will also produce a standing wave