Physics - Geometrical Optics Question with Solution | TestHub

PhysicsGeometrical OpticsRefraction+ReflectionEasy2 minPYQ_2020
PhysicsEasysingle choice

A cylindrical tube filled with water μw=43 is closed at its both ends by two thin, silvered plano-convex lenses, as shown in the figure. Refractive index of lenses L1 and L2 are 2.0 and 1.5, while their radii of curvatures are 5 cm and 9 cm, respectively. A point object is placed somewhere at a point O on the axis of the cylindrical tube. If it is found that all the images formed by multiple refractions and reflections coincide with the object, then the distance between both the lenses is

Options:

Answer:
B
Solution:

For the lens L1, the ray must move parallel to the axis after refraction, for the image to coincide with the object.

μ1+μwx=μ1 -μwR1, where x is the distance of the object from the lens L1

43x=2-435

x=10 cm

For the lens L2, the ray must appear to come from the centre of curvature after refraction, for the image to coincide with the object.

μ2-R2+μwy=μ1 -μw, where y is the distance of the object from the lens L2

y=R24332=8 cm

Distance between the two lenses = 10 cm + 8 cm = 18 cm

Stream:JEESubject:PhysicsTopic:Geometrical OpticsSubtopic:Refraction+Reflection
2mℹ️ Source: PYQ_2020

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