• Without light we cannot see object.
• range of visible electromagnetic radiation is 3800 A⁰ 7800 A⁰
Source of light :-
1. Luminous :-
The object which can be seen as they emits their own light are called luminous object.
Example - bulb, stars, Sun etc.
2. Non luminous :-
Those objects which can be observed only when the light scattered by then are called non luminous.
Example - book, pen, wood, table etc
Optics :-
The branch of science that deals with the nature of light is called optics.
Nature of light :-
• Light has dual nature
1. Particles nature
2. Wave nature
• light is a non mechanical (electromagnetic wave) wave as it does not require material medium.
• speed of light in vacuum is 3*10⁸ m/s.
• light travels along a straight lines in a medium or vacuum this is called rectilinear propagation of light.
• it's a path changes when there is an object in its path or where the medium change.
• straight line path of light is called light ray.
• bundles of light rays is called as beam of light.
• the medium in which light can travel over large distance is called a transparent medium.
Example - glass, water, air.
• the medium in which light can travel over short distances only and it's intensity rapidly such medium is called translucent medium.
• when the density of material medium increases, the speed of light decreases.
Reflection of light :-
the bouncing back of light after striking the surface in the same medium is called reflection of light.
Laws of reflection :-
1. The angles of incidence and the angle of reflection are equal.
2. incident light ray, the reflected light ray and the normal to the mirror at the point of incidence are in the same place.
Reflection by plane mirror :-
• Characteristics of image formed by plane mirror.
1. Distance of object from the mirror = distance of image from mirror.
2. The image is laterally inverted.
3. The size of the image is the same as that of the object.
4. Image is virtual and erect.
Reflection by spherical mirror :-
• A spherical mirror is a part of a hollow sphere.
It is of two types.
1. Concave mirror
2. Sunways mirror
Ray tracing :-
1. A ray going through centre of curvature is reflected back along the same direction.
2. A ray parallel to principal axis is reflected through the focus and vice versa, also mutually parallel rays after reflection intersect on the focal plane.
3. A ray going to the pole and the reflected ray from it make equal angles with the principal axis.
Use of a spherical mirror
Concave mirror :-
1. The reflectors of table
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