PhysicsHardHigh School (11–12)Optics › Lenses and Optical InstrumentsNEETAEEE (Amrita)AMUEEEAP EAPCETBCECECMI Entrance
Created by StemPy LabAssertion (A): A small air bubble inside a glass block has the shape of a double convex lens. A narrow parallel beam of light that travels through the block and falls on the bubble along its axis spreads out after passing through it. Reason (R): A lens of a given shape bends light towards its axis only if its material has a larger refractive index than its surroundings. If the material has a smaller index, the same shape bends light away from the axis.
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← A student has a thin double convex lens of refractive index 1.50. Its focal length in air is 15 cm. She holds it completely under a transparent liquid of refractive index 1.80 and sends a narrow beam of parallel rays from a distant lamp along its axis. What is the focal length of the lens in the liquid, and what does the lens do to the beam?Two thin lenses are placed in contact on a common axis. Four such pairs are listed in List-I, with the focal length of each lens. Match each pair with the power of the combination in List-II. A dioptre, D, is one per metre. List-I (Focal lengths of the two lenses) A. +20 cm and +20 cm B. +25 cm and -50 cm C. -10 cm and +40 cm D. +50 cm and -25 cm List-II (Power of the combination) I. +2.0 D II. -2.0 D III. -7.5 D IV. +10 D →
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