CHAPTER 18 - Elementary Principles of Geometric Optics

Abstract

This chapter discusses the elementary principles of geometric optics along with different measuring techniques and devices. Most bodies reflect light in irregular way called diffuse reflection. A virtual image of an object is one through points of which light does not actually pass but through which light only appears to have passed. The two laws of reflection are: (1) the angle of incidence is equal to the angle of reflection, (2) the reflected ray, the incident ray, and the normal ray at the point of incidence all lie in one and the same plane. When light passes from one medium, such as air into another such as glass then, unless the light strikes the boundary normally, the direction of travel of the light is changed. This is the phenomenon of the refraction of light. The chapter also highlights experimental results which reveal that when light passes through a succession of parallel boundaries among different media, emerging finally into the same medium as the initial medium, then the final angle of emergence is equal to the initial angle of incidence. When light travels from an optically denser medium across a boundary to an optically less dense medium, refraction is away from the normal.