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Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsOptical instrumentsMedium2 minQB

PhysicsMediumsingle choice

When a telescope is adjusted for parallel light, the distance of the objective from the eye-piece is found to be 100 cm for normal vision. The magnifying power of the telescope in this case is 9. If an old person cannot see beyond 90 cm and wishes to use the telescope then he will have to reduce the tube length by

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Answer:

Solution:

$f_{o} + f_{e} = 100 cm$ and $f_{o} / f_{e} = 9 \Rightarrow f_{o} = 90 cm, f_{e} = 10 cm$ . For a virtual final image at $90 cm : 1/ u_{e} = 1/ f_{e} + 1/90 \Rightarrow u_{e} = 9 cm$ . New tube length $= 90 + 9 = 99 cm$ ; reduce by 1 cm.

Stream:JEESubject:PhysicsTopic:Geometrical OpticsSubtopic:Optical instruments

⏱ 2mℹ️ Source: QB

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