In the given figure, the radius of curvature of curved surface for both the plano-convex and plano-concave lens is 10 cm and refractive index for both is 1.5. The location of the final image after all the refractions through lenses is
A
15 cm
B
20 cm
C
25 cm
D
40 cm
Hard
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Updated on : 2022-09-05
Solution
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Correct option is B)
The focal length of the plano - convex lens is:
f11=(1.5−1)(+101−∞1)=201
Focal length of plano - concave lens is:
f21=(1.5−1)(∞1−101)=−201
since parallel beams are incident on the lens, its image from plano - concave lens will be formed at +20cm from it (at the focus) and will act as an object for the plano - concave lens. since the two lens are at a distance of 10cm from each other, therefore, for the next lens
u=+10cm
v=u+fuf=10−2010×20
⇒v=(10200)cm=20cm Hence, the correct option is (B)
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