Chapter 3

Propagation of Light

• Propagation of Light• Formation of shadows• The shadow cast by a point source of light• The shadow cast by an extended source of light• Eclipses• The colours in sunlight• The Pin hole cameraght is necessary for the growth

of plants

Propagation of Light

• Light travels in a straight line.This is called Propagation of Light.

• Activities

• Formation of shadows• The shadow cast by a point source of light• The shadow cast by an extended source of

light

• Eclipses• Solar eclipses-if

the moon comes between the sun and the earth and the three are in a straight line,the shadow of the moon falls on the earth,then solar eclipse takes place.

• Lunar eclipses-if the earth comes in between the sun and the moon,the shadow of the earthfalls on the moon,then lunar eclipse takes place.

• COLOURS IN SUNLIGHT

• Violet • Indigo• Blue• Green• Yellow• Orange• Red

• The pin hole camera

• Light is necessary growth of plants

• QUESTION HOUR• 1Define linear propagation of light• 2Eclipses• 3Why does an object cast a shadow on a

screeen?• 4Give reason-The Penumbra is faint.• Define umbra and penumbra.