STRAIGHT OR BENT...THAT IS THE QUESTION
It has been shown that light travels in rays. Light also wants
to get to a certian destination in the shortest possible time.
Therefore, in order to accomplish that, regardless of how fast
the ray might be traveling, the light ray will bend to reach its
destination in the shortest amount of time. This theory is
known as Fermat's Principle.
Now depending on the type of material the light ray is entering
and leaving, determines how much the light slows down and the
new path of travel. When traveling from a high index of
refraction to a low index of refraction the light increases in
velocity and bends away from the normal. And when traveling
from a low index of refraction to a high index of refraction,
the light decreases in velocity and bends towards the
normal.
Each material has its own index of refraction. Some common
indicies of refraction include:
AIR 1.0003
WATER 1.33
ETHYL ALCOHOL 1.36
GLASS
-- QUARTZ 1.46
-- CROWN 1.52
-- FLINT 1.58
SODIUM CHLORIDE 1.53
LUCITE 1.57
DIAMOND 2.42
The angle at which the light is entering the second medium is called the
Angle of Incidence. The angle the light creates with the
normal after entering the second medium is called the Angle of
Refraction.
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The light ray travels from a low index of refraction to a high index of
refraction causing the ray to bend towards the normal.
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The diagram would be flipped 180 degrees if the
light was traveling from a higher index of refraction to a lower index of
refraction.
To determine the speed of light in each medium, you would divide the
speed of light in a vacuum by the index of refraction.
v = c/n
For example: if light is traveling through water, the speed would be
v = (3x10^8 m/s)/1.33
v = 2.23x10^8 m/s
You can use this equation to obtain the speed of light in various other
materials as well.
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