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Refraction Of Light
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If you place a pencil in a glass of
water, you will see that the pencil appears to be bent.
Now, you know for a fact that the pencil is not bent at all,
it just appears to be so. This is the effect of light.
Light is actually a form of energy called electromagnetic
radiation. There is a wide spectrum of radiation with
X-rays, ultraviolet rays, infrared rays etc. and most of them
are present in the atmosphere with their own definite
wavelengths and properties, but the only wavelengths
that we are able to see is that of Visible Light.
A Pencil Appears Bent In Water |
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Since light is in the form of electromagnetic waves, it has many
characteristic properties like reflection (this
helps us to see objects, because only when light reflects off an
object, we can see it), travels at different speeds in different
objects and most importantly, undergoes refraction. |
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The term refraction is defined as the
bending of light as it passes from one type of material into
another. Because light travels at different speeds in
the two materials, it changes its speed at the boundary of the
two materials. If a beam of light hits this boundary at an
angle, then light hitting the side first will be forced to
slow down or speed up before light on the other side hits the
new material. This causes the beam to bend, or refract, at the
boundary. Suppose we were to place a coin in a glass of water.
The light bouncing off the coin underwater, for instance,
would have to first travel through the water and then
the air to reach an observer's eye. At the boundary,
it gets refracted and reaches the observer's eye, thus
appearing to be slightly raised. |
A Coin Appears To be Slightly Raised In Water |
In the pencil case, the pencil is placed at
a specific angle and looks bent at the point where it touches the
water, because light coming from the submerged portion of
the pencil gets refracted as it crosses the water-air boundary.
The refractive index of a material is said to be
= the speed of light in empty space
the speed of light inside the material
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Depending on the quality of
the material and the more importantly the
light frequency, the speed of light will vary.
Therefore the refractive index is different for different
materials. This is how the colorful spectrum is created when
light passes through a glass prism - the light of
different colors gets bent at different angles as it passes
from one material to another. |
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Dispersion Of Light
Through A Prism |
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This property of light gives rise to many interesting
phenomenon such as submerged objects looking raised,
the mirage often seen in the desert, the twinkling of stars
(light beams go through refraction in the various layers of
the atmospheric air) and many more.
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