Light is a form of energy that enables us to see the things around us. Light travels along a straight line. Reflection of light takes place when light rays fall on the surface of an object and are bounced back into the same medium.
The rays reflected from an object make an optical representation of the object called image. An image which can be obtained on the screen is called a real image. The image which cannot be obtained on a screen is called a virtual image.
The images formed by a plane mirror are laterally inverted i.e., left side of an object in the mirror appears as right side and vice-versa and the phenomenon is called lateral inversion.
Some mirrors are spherical in shape. A spherical mirror in which the reflecting surface curves inwards is called a concave mirror. A spherical mirror in which the reflecting surface bulges out is called a convex mirror.
Most of the real images are obtained by using a piece of transparent refracting material which is bounded by the two surfaces known as lens. Spherical lenses are categorized as convex and concave lens. A convex lens is thicker at the center but thinner at the edges whereas a concave lens is thinner at the middle but thicker at the edges.
Images formed by spherical lenses have important characteristics and have wide application in optics. Another device called prism has a property to split a white beam of sunlight into seven colours. These seven colours can also be seen in a rainbow. Newton’s disc shows that the mixing of seven colours of light again results in the formation white colour.