# Refraction at plane surfaces

## The principle of reversibility of light

The principle of reversibility of light The principle of reversibility of light, which states that the paths of light rays are reversible, has already been mentioned in connection with reflection on page 237. The same holds true in the case of refraction and, indeed, for rays passing through any optical system. The refractive indices for a ray passing …

## Some effects of refraction

Some effects of refraction The apparent upward bending of a stick when placed in water is shown in Fig. 23.6. Rays of light from the end B of the stick pass from water to air, and are bent away from the normal, since they are passing to a less optically dense medium. Entering the eye, the rays appear …

## Geometrical construction for refracted ray

Geometrical construction for refracted ray The alternative method of treating the results of the last experiment suggests a way of finding the path of a ray through a glass block or some other medium, when i and n are given. Example. Trace the path of a ray through a glass block of refractive index 1.52, for light entering …

## Refractive index

Refractive index The value of the constant s;in i for a ray passing from one medium to another is called SID r the refractive index of the second medium with respect to the first; and is denoted by the symbol n. If, however, the first medium is air it is usual to speak of n simply as the …

## To investigate Snell’s law of refraction

To investigate Snell’s law of refraction A straight line SS’, to represent the surface of separation between air and glass, is drawn on a sheet of drawing paper on a drawing-board, together with a normal ON and several lines at various angles to ON to represent incident rays (Fig. 23.2). A ruler is placed along SS’ and a …

## The laws of refraction

The laws of refraction Although many scientists worked on the problem, the laws governing the refraction of light when it passes from one substance to another resisted discovery for centuries. It was not until 1621 that Willebrord Snell, Professor of Mathematics at Leyden University, discovered the exact relationship between the angles of incidence and refraction. The laws of refraction …

## Refraction at plane surfaces

Refraction at plane surfaces A pond or a swimming bath both appear much shallower than they actually are; a straight stick appears bent when partly immersed in water; and the landscape “shimmers” on a hot summer’s day. These, and many similar effects are caused by refraction, or the change in direction of light when it passes from one …