Page 1 - Lesson note refraction by spherical lens
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SAI INTERNATIONAL SCHOOL
PHYSICS
CLASS X
Chapter:LIGHT-REFLECTION AND REFRACTION
MODULE-29
Refraction of Light by Spherical Lens.
A lens is a transparent material bound by two curved surfaces. Lenses are broadly
classified into two categories depending on their surfaces.
Convex lens
A convex lens is made by joining two spherical surfaces in such a way that it is
thicker at the centre. Its thickness gradually reduces as we move towards the edge.
A convex lens has the ability to converge the light rays to a point that are incident on
it. Thus, it is called a converging lens.
A convex lens bulges outward and is thick at the center and thinner at the edges.
Convex lens converges the light rays as shown below in the figure 1(a).
Hence convex lenses are called converging lenses.
Concave lens
A concave lens is made by joining two curved surfaces in such a way that it is
thinner at the centre. Its thickness gradually increases as we move towards the
edge. A concave lens has the ability to diverge a beam of light rays incident on it.
Thus, it is called a diverging lens.
A concave lens bulges inward and is thinner in the middle and thicker at the edges.
Such lenses diverge light rays as shown in Figure 1(b)
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