A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is doubled of the other. Find the radii, if the refractive index of the material of the lens is 1.5. [NEET…

Question

A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is doubled of the other. Find the radii, if the refractive index of the material of the lens is 1.5. [NEET 2019]

Accepted Answer

Correct answer: C. (c) Using the lens Maker's formula 1f= ( _2- _1 _1 )( 1R_1- 1R_2) Here, f=25 cm , _2=1.5 , _1=1 (for air) let R_1=R and R_2=-2R ⇒ 125= ( 1.5-11 )( 1R-(- 12R)) 125 0.5= 1R+ 12R R= 32 25 0.5=18.75 cm ∴R_1=18.75 cm R_2=2 18.75=37.5 cm

$A double convex lens has focal length 25 cm. The radius of curvature of one of the surfaces is doubled of the other. Find the radii, if the refractive index of the material of the lens is 1.5. [NEET 2019]$

Solution

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