# Reflection

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```					                 Reflection
• The law of reflection
states that the angle
of incidence is equal
to the angle of
reflection.
• All angles are taken
from the normal line
not the surface!
Regular Reflection
• If all the normal lines
are parallel to each
other you get a
precise image.
Reflection
The image of a reflection
is virtual, erect, and
backwards.
Why is the front of an ambulance
written backwards?
Convex and Concave Images
• A convex mirror will
give you a upright
virtual and smaller
image.
• A concave mirror will
give you a real
inverted image if you
are beyond it focal
point.
Diffuse Reflection
• In Diffuse reflection
you are not able to
see a clear image
because the normal
lines are not parallel
to each other.
Example: white paper
light is reflected but
not like a mirror.
Refraction
• The bending of a wave as wave enters a new
medium.
• A medium is what the wave is in. ie. Water, air,
metal…
• n1 sinθ1 = n2 sin θ2
n = index of refraction
• The index of refraction is a ratio to the
speed of light in a vacuum vs. speed of
light in a substance. I like to think of it as
optical density!
• Air is 1.00
• Water is 1.33
• Lucite is 1.5
• Diamond is 2.42
Calculate the speed of light in a
substance.
•   n = c/v
•   c is speed of light (3.0 x 108 m/s)
•   Find the speed of light in water.
•   n = c/v
•   1.33 = (3.0 x 108 m/s) / v
•   v = 2.256 x 108 m/s
Diagram of refraction of water waves.
The source wave is encountering an
The straw seems to be          area of decreased water depth.
broken, due to refraction of
Notice how the bottom of the wave is
light as it emerges into the
moving slower than the top.
air.
Hence, you notice the bend.
Refraction
• As a wave enters a
new medium with a
larger index of
refraction the wave
slows down, the angle
decreases and the
wavelength gets
smaller.
• The frequency of the
wave does not
change!
Internal Reflection
• Sinθc = 1/n
• The critical angle is the
angle of incidence where
it causes the light to be
reflected at 90 degree to
the normal . If the angle
of incidence is greater
than the critical angle
you get total internal
reflection. ie. fiber optics.

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 views: 33 posted: 8/9/2011 language: English pages: 12