all defination for Lno.16 reflection of light
Answers
1. Ray of Light : A line drawn in the direction of propagation of light is called a ray of light.
2. Beam of Light : A group of rays of light emitted by a source of light is called a beam of light. A light beam is of three types.
(i) Parallel beam : A group of light rays parallel to each other is known as parallel beam of light.
(ii) Divergent beam : A group of light rays spreading out from a source of light is called divergent beam of light.
(iii) Convergent beam : A group of light rays meeting at a point is called convergent beam of light.
3. Reflection of Light : There are some surfaces which have ability to send the light back in the same medium when light strikes it. This phenomena of sending the light back in the same medium by a surface is called reflection of light.
(i) The incident ray, the reflected ray and the normal at the point of incidence, all lie in a same plane.
(ii) The angle of incidence is always equal to the angle of reflection, ∠i = ∠r.
4. Image : When light rays meet or appear to meet after reflection from a mirror,then it is called an image.
- Real Image : It is a kind of image which is formed by actual intersection of light rays after reflection.
- Virtual Image : It is a kind of image which is formed by producing the reflected rays backward after reflection.
5. Plane Mirror : Plane mirror is a piece of glass whose one side is polished by using silver paint, which is covered by a coating of red paint to protect the silver layer.
6. Spherical Mirrors : It is part of hollow glass sphere whose one surface is polished.
There are two types of spherical mirror.
(i) Concave Mirror : It is a spherical mirror whose outer surface is polished and inner or concave side is reflecting surface.
(ii) Convex Mirror : It is a spherical mirror whose inner is polished and outer side or convex side is the reflecting surface.
7. Principal Focus : A point on the principal axis of a spherical mirror where the rays of light parallel to the principal axis meet or appear to meet after reflection from the mirror.
8. Focal Length : The distance between the pole (P) and principal focus(F) of a spherical mirror is called the focal length of the mirror. It is denoted by f.
9. Uses of Concave Mirror :
(i) It is used as a shaving mirror because when it is placed close to the face, it forms a large image.
(ii) It is used in solar heating devices like solar cooker, because it converges Sun’s rays over a small area to produce high temperature.
(iii) It is used for security checking purposes.
10. Uses of Convex Mirror :
(i) It is used as rear view mirror in automobiles because it gives erect image as well as diminished due to which Pt has wider field of view.
(ii) It is also used in street lights.
11. Mirror Formula :
It is a relation between distance of object, distance ofimage from the pole ofthe mirror and it’s focal length, i.e., relation between ‘u’, ‘v and It is given by : 1/f = 1/u + 1/v.
12. Magnification : It is defined as the ratio of height of image to the height of the object. It is denoted by letter m.