Reflection of light one Shot Revision Notes:

 Reflection of light one Shot Revision Notes:

*Light is a form of energy which gives us sensation of vision.
*Light itself is invisible but makes the thing visible.
*Visible light is electromagnetic radiation belongs to a particular part of electromagnetic       spectrum.
*The object which has its own light is said to be luminous object.
*Ex: sun, lamp, bulb etc. In our day to day life, we see several phenomena associated with light   i.e. twinkling of stars, image formation, rainbow colours etc.                             

 Properties of light:

1. Light is an electromagnetic wave so it doesn’t require any material medium for travel. 

2. It possess both particle as well as wave Light takes straight path for their travel.

3. It also causes shadow formation.

4. The speed of light is 3,00,000 kilometres per second.

5. Colour phenomena is also caused by the presence of light.

6. Reflection, refraction and absorption are observed in case of incidence of light on any surface. 7. Ray of light is the line drawn in the direction of propagation of light.

8. The beam of light is the bundle or group of rays emitted from a source together.

There are three types of beam of light:

Laws of reflection:

There are two laws of reflection. 

These laws are applicable for all types of reflecting surfaces. 

They are: 

The angle of incidence is always equal to the angle of reflection. i.e. ∠i = ∠r 

The incident ray, the reflected ray and normal to the plane at the point of incidence, all lie in the same plane.

Types of mirror:

There are two types of mirrors. They are plane and spherical mirrors. 

I. Plane mirror:

A plane (flat) glass polished with silver paint on either side is said to be plane mirror. 

A coat of red paint is required over the silver polish to protect silver layer.

Image formation by a plane mirror: 

1. When two rays actually meet or appears to meet at a point then image is formed.

2. A plane mirror always forms virtual and erect.

3. The distance of object from the mirror is same as the distance of the image of the mirror.

4. Size of image and the object is same.

5. A plane mirror forms laterally inverted.

II. Spherical Mirrors:

There are two types of spherical mirrors:

Concave mirror: A spherical mirror whose reflecting surface is curved inwards is said to be concave mirror. It is also called converging mirror as it converges parallel beam of light falling on it. 

Convex mirror:A spherical mirror whose reflecting surface is curved outwards is said to be convex mirror. It is also called diverging mirror as it diverges parallel beam of light falling on it.

Important terminology:

Principal axis: Pole and center of curvature is joined by a line called principal axis.

Pole: The center of the mirror is pole. We denote it by ‘P’. 

Center of curvature: The center of the sphere which mirror is a part is center of curvature. It is denoted by ‘C’.

Radius of curvature: The radius of the sphere which mirror is a part is radius of curvature. The distance between pole and centre of curvature.

Focus: When parallel light beam is incident on the spherical mirror, then after reflection, the point at which they meet or appears to meet is said to be focus of that mirror.

Focal length: The length of the line joining pole and focus of the spherical mirror is its focal length. It is denoted by the symbol ‘f’.

Ray diagram: 

There are certain rules we should follow to make ray diagrams which will further used in understanding light reflection and refraction.

** A beam of parallel rays incident on spherical mirror after reflection passes through focus. 

In case of concave mirror the reflected ray converges to focus but in case of convex mirror the ray appears to diverge from focus. 

The incident ray when passes through focus after reflection it passes parallel to the principal axis. 

A ray incident on the spherical mirror passing through center of curvature returns back on same path. 

A ray incident to the pole of the mirror after reflection makes equal angle with the principal axis.

Uses of concave mirror:

 1. It is used in search lights, vehicle headlights, torch.

2. We use it as a shaving mirror.

3. It is used by doctors (dentists) to see the enlarged image of the teeth.

4. In solar furnace large concave mirrors are used to converge solar heat at a single point. 

   Uses of convex mirror: 

1. Convex mirror is used as the rear view mirror as it covers wide view and the image is always erect.

2.In shops it is used as the security mirror. Now CCTV does the same.

3. At danger traffic turns it is used to see the opposite comers.