When light travelling in one transparent medium encounters a boundary with a second transparent medium (e.g., air and glass), a portion of the light is reflected, and a bit is transmitted into the second medium. As the transmitted light moves into the second medium, it changes its direction of travel; i.e., it is refracted—the law of refraction, also known as Snell’s law. Light is a source of energy which generates a sensation of vision in human beings. Light seems to travel in straight lines. The different types of a spherical mirror, convex and concave are taught. The various terms related to spherical mirrors like the centre of curvature, the radius of curvature, focus, pole, etc. are discussed with ray diagrams. Uses of a spherical mirror are also discussed in this chapter. Mirror formula gives the relationship between the object-distance, image-distance, and focal length of a spherical mirror. The focal length of a spherical mirror is equal to half its radius of curvature.
Refraction is the bending of a wave when it enters a medium where its speed is different. The refraction of light when it passes from a fast medium to a slow medium bends the light rays toward the normal to the boundary between the two media.