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Asked in NEET 2023 Manipur · Total internal reflection and optical fibres
Given: white light inside the glass meets the top face, and the green component leaves grazing along that surface.
Idea: a ray that emerges along the surface is at exactly its own critical angle, so here the angle of incidence equals C for green.
sin C=1/μ, and μ falls as the wavelength rises, so C rises with wavelength.
Yellow, orange and red are longer in wavelength than green, so their critical angles are larger than the angle of incidence and they refract out.
Blue and violet are shorter in wavelength, have larger μ and smaller C, so they are totally internally reflected.
The set that comes out in air is yellow, orange and red.
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