Reflection and Refraction of Light
11-12
The Interaction of
Light and Matter
Absorption, Transmission,
and Reflection
• Light Can do Three Things:
• 1) Absorb
• 2) Transmit or Refract
• 3) Reflect
Reflection and Refraction of Light
2
The Interaction of
Light and Matter
Absorption, Transmission,
and Reflection
• The opaque
material in this
candleholder only
absorbs and reflects
light—no light
passes through it.
Reflection and Refraction of Light
2
Absorption, Transmission,
and Reflection
• Materials that allow some light to pass
through them,
are described as
translucent.
Reflection and Refraction of Light
2
Absorption, Transmission,
and Reflection
• Transparent materials, such as this
candleholder transmit almost all the light
striking them,
so you can see
objects clearly
through them.
Reflection and Refraction of Light
2
Reflection of Light
Regular and Diffuse Reflection
• A smooth, even surface such as a pane of glass
produces a sharp image by reflecting parallel
light waves in only one direction.
• Reflection of light waves from a
smooth surface is regular reflection.
• To cause a regular reflection, the
roughness of a surface must be less
than the wavelengths it reflects.
• Ex: LOOKING IN A MIRROR
Reflection and Refraction of Light
2
Regular and Diffuse Reflection
• Reflection of light from a rough surface
is diffuse reflection.
• Diffuse reflection is a type of scattering
that occurs when light waves traveling in
one direction are made to travel in many
different directions.
• Ex: white cloth
Reflection and Refraction of Light
2
Refraction of Light
• Refraction is
caused by a
change in the
speed of a
wave when it
passes from
one material
to another.
Reflection and Refraction of Light
2
Refraction of Light
• Index of refraction is the ratio of the speed
of light in a vacuum to the speed of light in
the material.
• The index of refraction indicates how much
the speed of light is reduced in the material
compared to its speed in empty space.
• The larger the index of refraction, the
more light is slowed down in the material.
Reflection and Refraction of Light
2
Refraction of Light
• White light, such as sunlight, is made up
of light waves with range of wavelengths.
• Prisms refract the
light twice—once
when it enters the
prism and again
when it leaves the
prism.
Reflection and Refraction of Light
2
Refraction of Light
• The longer wavelengths of light are slowed
less and are bent the least.
• As a result, the
different colors
are separated
when they emerge
from the prism.
Reflection and Refraction of Light
2
Diffraction of Light (10-3)
• Occurs when an object causes a wave to
change direction and bend around it.
• The amount of
diffraction that
occurs depends on
the size of the object
• If the object is
smaller than the
wavelength then the
wave will bend
around it
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