Points to Remember-Class 10 -Science Physics-Chapter 10 – Light – Reflection and Refraction

Class 10 -Science-Points to Remember- Physics-Chapter 10 – Light – Reflection and Refraction

IMPORTANT POINTS TO BE REMEMBER 

◆ Laws of reflection :   (a)  Angle of incidence is equal to the angle of reflection .  (b)  The incident ray, the reflected ray and the normal all lie in the same plane.  

◆ Mirror : A smooth, highly polished reflecting surface is called a mirror. There are two types of mirrors : (a) plane mirror (b) curved mirrors   Curved mirrors are classified as spherical mirrors or parabolic mirrors depending upon the curvature of the mirror. 

◆ Concave mirror : A spherical mirror whose inner hollow surface is the reflecting surface is called concave mirror. A concave mirror forms a real, inverted image of an object if the object is placed at any place outside F. However, when  the object lies between F and P, the image formed is erect and virtual. 

◆ Convex mirror : A spherical mirror whose outer bulging at surface is the reflecting surface is called convex mirror. The image formed by a convex mirror is always erect, virtual and smaller than the object whatever may be the position of the object. A convex mirror is used as a side-mirror (driver’s mirror) on automobiles. 

◆ Aperture of a mirror : The effective width of a spherical mirror from which reflection can take place is called its aperture. 

◆ Pole : The centre of a curved mirror is called its pole. 

◆ Centre of curvature : The centre of the hollow sphere of which the spherical mirror is a part is called its centre of curvature. The centre of curvature of a concave mirror is in front of it, while that of a convex mirror is behind it. 

◆ Radius of curvature : Radius of the hollow sphere of which the mirror is a part is called its radius of curvature. 

◆ Principal axis : A straight line passing through the centre of curvature and pole of a spherical mirror is called its principal axis.

◆Focus : A point on the principal axis of a mirror at which the rays coming from infinity meet or appear to meet is called its focus. Focus is denoted by F. 

◆ Focal length : The distance between the pole of a spherical mirror and the focus is called the focal of a spherical mirror. 

◆ Real image : The image which can be obtained on a screen is called a real image. A real image is formed only when the reflected or refracted rays actually meet at a point. 

◆ Virtual image : The image which can be seen into a mirror but cannot be obtained on a screen is called a virtual image. A virtual image is formed only when the reflected or the refracted rays appear to come from a point.

◆ Sign convention for spherical mirrors :    According to the sign convention for mirror, the focal length of a concave mirror is negative and that of a convex mirror is positive.

◆Mirrors formula : The relationship, 1/f = 1/v + 1/u is called the mirror formula.