# A point source of light S is placed at the bottom of a vessel containing a liquid of refractive index 5//3. A person is viewing the source from ab

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A point source of light S is placed at the bottom of a vessel containing a liquid of refractive index 5//3. A person is viewing the source from above the surface. There is an opaque disc of radius 1 cm floating on the surface. The centre of disc lies vertically above the source O. The liquid from the vessel is gradually drained out through a tap. What is the maximum height of the liquid for which the source cannot be seen at all.
A. 1.50 cm
B. 1.64 cm
C. 1.33 cm
D. 1.86 cm

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