Light: Electromagnetic Waves

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Light Electromagnetic Waves
?Direction of travel of the wave ? Electric field
? Magnetic field
? All perpendicular to each other ? Transverse
wave
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C299792458 m/s ? 3 x 108 m/s
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Reflection
Angle of reflected ray Angle of incident ray
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Refraction
n1
n2
Snells Law
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Chromatic Dispersion
Index of refraction depends on wavelengths of
light.
Blue light larger index of refraction Red light
Smaller index of refraction
Monochromatic light light of a single
wavelength or color
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A beam of monochromatic light reflects and
refracts at point A on the interface between
material 1 with index of refraction n11.33 and
material 2 with n21.77. The incident beam makes
an angle of 50o with the interface. What is the
angle of reflection at point A?
(a) What is the angle of refraction at point
A? (b) What is angle of refraction at point B?
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When the rectangular metal tank is filled to the
top with an unknown liquid, an observer with eyes
level with the top of the tank can just see the
corner Ea ray that refracts toward the observer
at the top surface of liquid is shown. Find the
index of refraction of the liquid.
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Total Internal Reflection
For angles of incidence larger than critical
angle ?C, all the light will be reflected.
?Total internal reflection
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A ray enters a glass slab at point A and then
undergoes total internal reflection at point B.
What minimum value for the index of refraction of
the glass can be inferred from this information?
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Polarization
The plane containing the electric vectors plane
of oscillation
Plane -polarized in the y-direction
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Polarizer When a light passes through a
polarizer, only the electric field component
parallel to the polarizing direction of the
polarizer can be passed.
For the light reaching a polarizer is
unpolarized, the intensity of the emerging
polarized light I is
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A system of three polarizing in the path of
initially unpolarized light. The polarizing
direction of the first sheet is parallel to the y
axis, that of the second sheet is 60o
counterclockwise from y axis, and that of the
third sheet is parallel to the x axis. What
fraction of the intensity Io of the light
emerges from the system, and is the light
polarized?
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Initially unpolarized light is sent through
three polarizers whose polarizing directions
makes angles of ?1 40o, ?2 20o, ?3 40o with
the direction of the y axis. What percentage of
the lights initial intensity is transmitted by
the system?
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Polarization by Reflection
When the light is incident at a particular
incident angle, the reflected light has only
perpendicular components (fully polarized.)
?This incident angle Brewster angle
Condition