Chapter-9.pmd - leph201.pdf
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R EFLECTION OF LIGHT BY SPHERICAL MIRRORS
R EFLECTION OF LIGHT BY SPHERICAL MIRRORS
R EFLECTION OF LIGHT BY SPHERICAL MIRRORS
T OTAL INTERNAL R EFLECTION When light travels from an optically denser medium to a rarer medium at the interface, it is partly reflected back into the same medium and partly refracted to the second medium. This reflection is called the internal reflection. When a ray of light enters from a denser medium to a rarer medium, it bends away from the normal, for example, the ray AO1 B in Fig. 9.12. The incident ray AO1 is partially reflected (O1 C) and partially transmitted (O1 B) or refracted, the angle of refraction (r ) being larger than the angle of incidence (i ). As the angle of incidence increases, so does the angle of refraction, till for the ray AO3 , the angle of refraction is π/2. The refracted ray is bent so much away from the normal that it grazes the surface at the interface between the two media. This is shown by the ray AO3 D in Fig. 9.12. If the angle of incidence is increased still further (e.g., the ray AO4 ), refraction is not possible, and the incident ray is totally reflected.
5.1 Refraction at a spherical surface
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