Reflection

Reflection. Radiation falling upon any bright surface is either partially or totally reflected, according to the nature of the surface. It will be simplest to consider the reflection of that particular form of radiation which we call light. If we let a beam of light fall upon a polished surface - say, a plane mirror - we shall note that the reflected beam , and incident beam are in the same plane with the normal to the mirror at the point of incidence, and both beams make the same angle with this normal. If the mirror be perfectly smooth and bright, it would only be able to reflect light in this regular manner; hence it would give us images of other bodies, but would itself be invisible. Bodies, however, do not usually reach this state of perfect polish, but irregularities in the surface cause the light to be irregularly reflected. Every incident ray is reflected according to the above laws, but differences in inclination of a multitude of small surfaces making up the whole, produce the effect of the light being reflected in all directions. This is what is known as diffusion of light, and it is in virtue of this that a body becomes visible. A plane mirror produces an image behind it exactly similar in size and shape to the object in front. Thus, let A B be an object in front of h, mirror, M m' (Fig. 1). A pencil of rays, A P, starting from A, is reflected in the direction P E, and appears to the eye (E) of an observer as though it came from a point a'.

Similarly the pencil b