Light- Reflection and Refraction

Chapter 10: Light- Reflection and Refraction

1.  When light falls on a body, it may be absorbed, may be transmitted or light may come back to the same medium.

2.  Reflection of a light means light waves are neither transmitted nor absorbed but are deflected from the surface of the medium back into the same medium. 

3.  Laws of Reflection :

First law of reflection: The incident ray, the normal to the surface at the point of incidence and the reflected ray, all lie in the same plane.

Second law of reflection: The angle of incidence is equal to the angle of reflection.

4.  Real image is obtained when the rays of light after reflection, actually converge at a point. It can be obtained on the screen and can be seen with the eye.

5.  Virtual image forms when rays of light do not actually meet, but appear to meet when produced backwards. It cannot be obtained on the screen.

6.  Characteristics of the image formed by the plane mirror :

i.            The image formed by a plane mirror is always virtual and erect.

ii.           Size of image = Size of object and the image is laterally inverted.

iii.         The image formed by the plane mirror is as far behind the mirror as the object is in front.

7.  Lateral Inversion: The phenomenon due to which the right side of the object appears as left and the left side of the object appears as right. That is the image is inverted sideways.

8.  A spherical mirror whose reflecting surface is curved outwards and polished on the inner spherical surface is convex mirror.

9.  A spherical mirror whose reflecting surface is curved inwards and polished on the outer spherical surface is concave mirror.

10.                Concave mirror mostly forms real images, which can be received on the screen.

11.                Convex mirror forms virtual images, which cannot be received on the screen.

12.                Differentiating between a plane mirror, a concave mirror and a convex mirror, without touching them:

i)              If the image formed is erect and is of same size as in reality then it is a plane mirror.

ii)            If the image formed is still erect but smaller in size then it is a convex mirror.

iii)           If the image is erect but magnified when mirror is close to the object then it is a concave mirror.

13.  Solar concentrators use huge concave mirrors to focus large amounts of solar energy thereby producing high temperature conditions in a solar power plant.

14.  Concavemirrors are used as shaving and make up mirrors.

15.  The centre of the reflecting surface of a spherical mirror is a point called the pole of the mirror and usually represented by P.