Dispersion of Light
Maqbool Chaudhry
Dispersion of light
• 'Dispersion of Light' can be defined as the splitting of white light when it
passes through a glass prism into its constituent spectrum of colors (i.e.
violet, indigo, blue, green, yellow, orange and red).
• Refraction is the bending in the path of the light when it travels from one
medium to the another. The degree at which refraction will occur depends
on the wavelength of the light. Each light wave has a different wavelength
and will therefore deviate differently. Red has the highest wavelength and
violet the lowest.
• Wavelength is inversely proportional to the deviation in the path of the
light. Red light suffers the least amount of deviation and violet the most.
When a white light is made to pass through a prism, formation of a
spectrum of seven colors occurs showing white light is a combination of
seven separate colors.
• Prism only acts as a medium for the dispersion of light made of the seven
colors. Refraction occurs when the light falls on the prism. The wavelength
and frequency of these deviated colors is different, they deviate differently
at different angles due to the velocity difference of the prism. The color
red therefore deviates the least since it has maximum wavelength and
color violet deviates the most since it has the least wavelength.
Recombination of colors:
The Newton disc, also known as the
Disappearing Color Disc, is a well-known
physics experiment with a rotating disc with
segments in different colors (usually Newton's
primary colors: red, orange, yellow, green, blue,
indigo, and violet) appearing as white (or offwhite or gray) when it spins very fast.
Monochromatic light: It is a light of single wavelength (one
colour). Yellow light obtained from a sodium lamp looks nearly
monochromatic but infact it is also a mixture of two nearly equal
wavelengths. Generally it is impossible to produce completely
monochromatic light.
Polychromatic light: It is a light consisting of several colors
Color: it is a property of light which depends entirely on its frequency.
Appearance of objects in colored light
Spectrum
These waves propagate through space at different
radio frequencies, and the set of all possible
frequencies is called the electromagnetic spectrum.
Perhaps the most familiar part of the
electromagnetic spectrum is the visible light
spectrum.
Light spectrum can mean the visible spectrum, the
range of wavelengths of electromagnetic radiation
which our eyes are sensitive to… or it can mean a
plot (or chart or graph) of the intensity of light vs its
wavelength.
Types of spectrum:
• A spectrum in which there
is overlapping of different
colors is called an impure
Spectrum. In other words,
in an impure spectrum, the
colors are not distinct and
independent but they
overlap.
• A spectrum with each color
distinct and independent is
called a pure spectrum.
Electromagnetic spectrum:
• The electromagnetic (EM) spectrum is the range of all types of
EM radiation. Radiation is energy that travels and spreads out
as it goes – the visible light that comes from a lamp in your
house and the radio waves that come from a radio station are
two types of electromagnetic radiation. The other types of EM
radiation that make up the electromagnetic spectrum are
microwaves, infrared light, ultraviolet light, X-rays and
gamma-rays.
Electromagnetic Waves(EM Spectrum)
Visible light Optical fibres:
Light is used in optical fibres for medical purposes and
telecommunications.
Uses of EM spectrum:
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Radiowaves:
Radio communication
Radar
Radio navigation systems
Communications satellites
Wireless computer
networks
• They are able to go around
obstructions due to their
longer wavelength
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Microwave:
Wireless networks
Radar
Satellite
Spacecraft communication
Cancer treatment
Radio astronomy
Industrial heating
Garage door openers
For cooking food in
microwave ovens.
• MW can penetrate through
light rain, snow, clouds and
smokes
• Infrared:
• Remote controls
• Fiber optic cables
• Sun emits infrared
• Create and conduct heat
• Sunbed
• Security light sensor
• Night vision equipment
• Ear thermometer used to
detect the IR radiations
given out by human body.
• Intruder alarm
• UV-rays:
• Causes skin to tan
• Increases risk of skin
cancer
• Kills bacteria in food and
water
• Stimulate production of
vitamin D
• Fluorescent Lamps
• Security marking
• Sterlization
• Used in sunbeds for
artificial tanning
• X-ray:
• Checking for fractures
(broken bones).
• to destroy cancer cells
• In airports to examine
luggage(scanners).
• Detect cracks in metal
objects
• Study of space
• Radiotherapy
• Gamma rays:
• Sterilize food and
medical equipment.
• Radiotherapy
• Ray astronomy.
• It can be used to treat
cancer.
These high energy rays
are directed at cancerous
tumors to kill cancer cells.
The equation for wave, V=fλ
Maqbool Chaudhry