Light

Light

For 5th to 7th grade

Light explanation

Light is a form of energy that helps us to see everything around us . It does not require a medium and can travel even in vacuum. Let us look at some properties of light such as rectilinear propagation and reflection.

The meaning of rectilinear propagation of light.

Observe how the light from a torch travels in a straight line. The property of light travelling in a straight line is known as rectilinear propagation of light.

Difference between real image and virtual image

Real images formed by a single mirror ( or lens , as you will read later) are always inverted ( upside down ) .

A virtual image is always erect (upright), and virtual images cannot be formed on a screen.

The different kinds of mirrors

Convex mirror

Concave mirror

Difference between convex and concave mirrors.

The outside of a spherical mirror is silvered , it is called a concave mirror. The reflecting mirror curves inwards from the surface of the concave mirror.

If the inside of a spherical mirror is silvered , it is called a convex mirror. The reflecting surface of the convex mirror curves outwards.

• The pole(p) of a spherical mirror is the centre of the spherical mirror.

• The centre of curvature (C) of a spherical mirror is the centre of the sphere of which the mirror forms a part.

• The radius of curvature (r) of a spherical mirror is the radius of the sphere of which the mirror forms a part.

• The principal axis of a spherical mirror is the line joining the pole and the centre of curvature of the mirror.