• Reflection
happens when a wave
bounces back after hitting a barrier.
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Light waves reflecting off an object
allow you to see that object. A
reflected sound wave is called an
echo.
• Refraction
is the bending of a
wave as the wave pass from one
medium to another at an angle.

When a wave moves from one
medium to another, the
wave’s speed and wavelength
changes.
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Video
Refraction also depends
on the density of the
medium through which
light is passing.

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Diffraction is the spreading out
of waves through an opening or
around the edge of an obstacle
The edges of a shadow appear
fuzzy because of diffraction.
The light waves spread out, or
diffract, around the object that
is making the shadow.
Video
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Waves adding
together
The waves' crests and
troughs are aligned
briefly, which means
they join up exactly
Amplitudes are added
together

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Waves canceling each other out
The crest of one wave joins
briefly with the trough of the
other. The energy of one wave is
subtracted from the energy of
the other

Video