DISPERSION OF LIGHT The dispersion of light is the phenomenon of splitting of a beam of white light into its seven constituent colors when passed through a transparent medium.

DEVIATION PRODUCED BY PRISM The deviation produced by a prism depends upon: Angle of incidence (i) Angle of prism (A) Refractive medium of the material of prism () Wavelength of light used ()

CAUSES OF DISPERSION Higher the frequency, higher is the deviation. Like red color deviates less due to less frequency or more wavelength. NOTE: The color of the light depends upon its frequency, not its wavelength.

EM WAVES EM waves are a special type of wave that can travel without a medium. Unlike sound waves and water waves, electromagnetic waves don't need a fluid, or a solid, or even air to help them travel from one place to another. Electromagnetic waves are named for the fact that they have both an electric and a magnetic component.

EM SPECTRUM The orderly distribution of electromagnetic radiations according to their frequency or wavelength is called electromagnetic spectrum.

COMMON PROPERTIES OF ALL EM WAVES They are produced by accelerated charged particles. They do not require any medium to travel. They travel with speed of light.

LIST OF EM WAVES Radio Waves: Instant Communication Microwaves: Data and Heat Infrared Waves: Invisible Heat Visible Light Rays Ultraviolet Waves: Energetic Light X-rays: Penetrating Radiation Gamma Rays: Nuclear Energy

RADIO WAVES They are used in standard broadcast radio and television, shortwave radio, navigation and air-traffic control, satellite communication, RADAR system, radio telescopes, cellular telephones, and even remote-controlled toys. 

MICROWAVES Microwaves are extremely widely used in modern technology. They are used in radar system used in aircraft navigation, in long distance communication, in microwave ovens, in speed guns used in tennis and cricket to detect speed of the ball and of an automobile on road.

INFRARED WAVES These waves are produced by hot bodies like the stars, the sun, fire etc. They are used to treat back pain, muscle strain etc., have an important role in keeping Earth warm via green house effect, also used in remote switch and remote control systems in TV sets, video recorder, etc.

VISIBLE LIGHT It is the part of EM spectrum that is detected by human eye. Sun is the biggest source of visible light that enables us to see the objects around us.

ULTRAVIOLET WAVES UV waves are produced by very hot objects and special lamps. Sun is also a big source of UV rays. These waves are used to kill germs, viruses, bacteria, and small insects, so it is used as a disinfectant and for sterilizing surgical instruments. We protect our eyes from these waves during welding.

X RAYS They are also known as roentgen rays. They can pass through the bones as they are highly energetic waves. They can kill germs and bacteria and are used in certain forms of cancer. Used to detect cracks in metals, and to detect defects in automobile tires, tennis balls and detecting pearls in oysters.

GAMMA RAYS These waves are of nuclear origin and are used in medical field to destroy cancer cells (radio therapy) and to trigger off certain nuclear reactions.

SCATTERING OF LIGHT Scattering of light is the absorption and re-emission of light waves.

EXAMPLES AND APPLICATIONS OF SCATTERING OF LIGHT The color of clear sky is blue because the blue color of white light spectrum is scattered most. The color of sky in space is black because of absence of air in space due to which there is no scattering of light. Water in lakes and oceans looks blue because blue color is most scattered by the water molecules. Danger signals are red because red color has maximum wavelength and is least scattered.

SUN APPEARS TO BE RED DURING SUNRISE AND SUNSET Generally Sun appears yellow, but at the time of sunrise and sunset it appears to be reddish because the Sun during this time is at the horizon and the sun rays have to travel maximum distance due to which the low wavelength colors get scattered during the passage and red color is able to reach the eyes of the observer, so the sun and the sky appears red.

RANGE OF EM WAVES EM WAVE WAVELENGTH (in m) FREQUENCY (Hz) RADIO WAVES 10³ 3*101 to 3*109 MICRO WAVES 10¯² 3*109 to 3*1011 INFRARED WAVES 10¯⁴ 3*1011to 4*1014 VISIBLE LIGHT 10¯⁶ 4*1014 Hz to 8*1014 ULTRAVOILET RAYS 10¯⁸ 8*1014 to 3*1016 X-RAYS 10¯¹⁰ 3*1016 to 3*1019 GAMMA RAYS 10¯¹² 3*1019