# If radii of curvature of both convex surfaces is 20 cm then focal length of lens for an object placed in air in given arrangements

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If radii of curvature of both convex surfaces is 20 cm then focal length of lens for an object placed in air in given arrangements

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Given: If radii of curvature of both convex surfaces is 20 cm,
To find the focal length of the lens for an object placed in air in the given arrangement
Solution:
Using the formula for the refraction through curved surface for first surface, we get

Using the formula for the refraction through curved surface for second surface, we get

is the focal length of the lens for an object placed in air in the given arrangement