Light is the main focus of this unit. We shall describe different phenomena of light such as reflection, refraction and total internal reflection. We will learn how images are formed by mirrors and lenses and will discuss working principle of compound microscope and telescope.
12.1 REFLECTION OF LIGHT
Reflection of light is illustrated in Fig. 12.1. When a ray of light from air along the path AO falls on a plane mirror M, it is reflected along the path OB. The ray AO is called incident ray while the ray OB is called reflected ray. The angle between incident ray AO and normal N, i.e., 8 AON is called the angle of incidence represented by i. The angle between the normal and the reflected ray OB, i.e., 8 NOB is called angle of reflection represented by r.
Now we can define the phenomenon of reflection as:
When light travelling in a certain medium falls on the surface of another medium, a part of it turns back in the same medium.