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Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsTIR/Prism and DispersionMedium2 minQB

PhysicsMediuminteger

A point source of light is placed 6m below the surface of water of refractive index 5/3. The minimum diameter (in m) of a disc which should be placed over the source on the surface of water to cut-off all light coming out of water is :-

Answer:

Solution:

Rays grazing the disc edge hit the surface at the critical angle: $sin C = \frac{1}{μ} = \frac{3}{5}$ , so $tan C = \frac{3}{4}$ .

Disc radius $r = 6 tan C = 4.5$ m, so the minimum diameter is $2 r = 9$ m.

Stream:JEESubject:PhysicsTopic:Geometrical OpticsSubtopic:TIR/Prism and Dispersion

⏱ 2mℹ️ Source: QB

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