Light : What is Light ?

Importance of Light• Sunlight powers all light on earth,

either directly or indirectly. Plants obviously must have sunlight or full-spectrum artificial light to manufacture their food by photosynthesis.

• For diurnal species (species that are active during the day), light is important for many reasons. Obviously, it is required for vision, and most birds have highly developed sight. For many species of animals, full-spectrum light is required for the conversion of cholesterol to vitamin D.

• People living in northern cities that

are overcast for long periods of time and receive little sunshine typically report depression.

Properties of Light• The Reticulate Property of light: Light travels in a straight line.

• The speed of light is 300 million meters per second in a vacuum.

• Refraction means that light bends when it passes from one medium to another.

• When light enters a denser medium from one that is less dense, it

bends toward a line normal to the boundary between the two media.

• Dispersion is another property of light. This refers to the ability to break white light into its constituent colors.

Role in our daily lives• Study the picture given

alongside. This is Danish Architecture.

• Danish Architecture depends wholly on the direction of light

Look at the pic. Given alongside. His life is lightless.

Imagine living in a dark tunnel forever…..

Rainbow : Another form of light• Although light looks

colorless, it’s made up of many colors-red, orange, yellow, green, blue, indigo and violet. (VIBGYOR)

• These colors are known as the spectrum.

• When light shines into water, the rays of light refract, or bend, at different angles.

• Different colors bend at different angles--red bends the least and violet the most.

• When light passes through a raindrop at a certain angle, the rays separate into the colors of the spectrum-and you see a beautiful rainbow.

•

Newton Disc

• Newton disc is a disc with segments in rainbow colours.

• When the disc is rotated, the colors fade to white.

• In this way Isaac Newton demonstrated that white light is a combination of the seven different colours found in a rainbow.

• Newton disc is a disc with segments in rainbow colours.

• When the disc is rotated, the colors fade to white.

• In this way Isaac Newton demonstrated that white light is a combination of the seven different colours found in a rainbow.

Time for a whole new concept.

The Prism.

In optics, a prism is a transparent optical element with flat, polished surfaces that refract light.

The different theories of the prism’s action on light.

Before Isaac Newton, it was believed that white light was colorless, and that the prism itself produced the color.

Augustin - Jean Fresnel

Thomas Young

Lens – Convex• Lens such that a

beam of light passing through it is brought to a point or focus.

• A lens which has at least one surface which curves outwards.

• These lens are thinner at the edges and are thicker at the center.

Lens - Concave• A concave lens is thinner at

the center and thicker at the edges

• Also called diverging lens.

• These lens are such that a parallel beam of light passing through it is caused to diverge or spread out.

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