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A bi-convex lens is formed with two thin...

A bi-convex lens is formed with two thin plano-convex lenses as shown in the figure. Refractive index n of th efirst lens is 1.5 and that of the second lens if 1.2 Both the curved surfaces are of the same radius of curvature `R=14cm. ` For this bi-convex lens, for an object distance of 40cm, the image distance will be

A

`.280.0cm`

B

`40.0cm`

C

`21.5cm`

D

`13.3cm`

Text Solution

Verified by Experts

The correct Answer is:
B
`(1)/(f_(1))=(1.2-1)((1)/(oo)-(1)/(-14))=(0.2)/(14)`
`(1)/(f_(2))=(1.5-1)((1)/(14)-(1)/(oo))=(0.5)/(14)`
`(1)/(f_(eq))=(0.7)/(1.4)=(1)/(20)`
`(1)/(v)-(1)/(-40)=(1)/(20)`
`v=40cm`
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