Light
Light is a form of energy eyes. which produces the Sources of light are of three types-thermal sources and luminescent sources.
Photometry is a branch measurement of light energy.
Characteristics of Light
Light waves are electromagnetic waves, whose nature is transverse. The speed of light in vacuum is 3 x 10 8 mls but it is different in different media.
The speed and wavelength of light change when it travels from one medium to another but its frequency remains unchanged.
Important Terms
( i) Luminous Objects The objects which emits its own light, are called luminous objects, e. g., sun, other stars, an oil lamp etc.
( ii) Non-Luminous Objects The objects which do not emit its own light but become visible due to the reflection of light falling on them, are called nonluminous objects, e. g., moon, table, chair. trees etc.
( iii) Ray of Light A straight line drawn in the direction of propagation of light is called a ray of light.
( iv) Beam of Light A bundle of the adjacent light rays is called a beam of light.
( v) Image If light ray coming from an object meets or appear to meet at a point after reflection or refraction, then this point is called image of the object.