7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 1/12

Light Rays

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 2/12

  Luminous and Non LuminousLuminous Sources:

Emits its own lightExample-

Living things: fireflies and glow-worms

Non-living things: Sun, lighted candle ,electric lamp

Sources of LightTwo types:

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 3/12

Radiate light when their atoms are excited by some source

of energy.

Example: A torch shines as a result of the chemicalenergy stored in the batteries.

Non-Luminous Sources:Reflects light from a luminous sourceExample: Moon ,table ,pen

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 4/12

Light Amplification byStimulatedEmission of

Radiation

Emits a narrow, strong and concentrated bright

beam of light due to the excitation of the atoms.

 Applications:Medical Field- operations on eye and ear

CD players

Surveying and Ranging

Barcode Scanners

Welding and Cutting

Fibre optic communication

Laser Printing

LASER

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 5/12

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 6/12

Rays and BeamsRay: Direction along which light energy travels.

Beam: Stream of light.Collection of rays.

Classification of Beams:

 

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 7/12

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 8/12

Reasons for formation of shadows:

i. Opaque objects -do not allow light to pass throughthem

ii. Straight line property of light

Shadows

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 9/12

Parts of Shadow :Umbra: Innermost and darkest part of a shadow

Penumbra: Ring of partial shadow

Sharpness of shadow depends on size of light

sources .

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 10/12

Source Types :

 A. point source: Shadow with Umbra only

B. extended source: Shadow with Umbra and Penumbra.

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 11/12

What type of source is this ????

7/17/2019 Light Rays

http://slidepdf.com/reader/full/light-rays-568c263f0f767 12/12

Speed of Light