Plot a graph to show variation of the angle of deviation as a function of angle of incidence for light passing through a prism

CBSE Class 12 CBSE Class 12 Physics
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(i) Plot a graph to show variation of the angle of deviation as a function of angle of incidence for light passing through a prism. Derive an expression for refractive index of the prism in terms of angle of minimum deviation and angle of prism.
(ii) What is dispersion of light ? What is its cause ?
(iii) A ray of light incident normally on one face of a right isosceles prism is totally reflected as shown in fig. What must be the minimum value of refractive index of glass ? Give relevant calculations.

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Plot a graph to show variation of the angle of deviation as a function of angle of incidence for light passing through a prism.png285×501 14.8 KB

(ii) Dispersion of light is the phenomenon of . splitting up of white light into its constituent
colours.
Cause of dispersion : The different colours of light are due to different wavelengths. The wavelength of violet light is smaller than that of red light. Since refractive index varies with different wavelength, thus different wavelengths take different paths and hence get split into the constituent colours.