A double convex lens made of glass has both radii of curvature of magnitude 20 cm . Incident light rays parallel to the axis of the lens will converge to a point at a distance ' L ' from the

Question

A double convex lens made of glass has both radii of curvature of magnitude 20 cm . Incident light rays parallel to the axis of the lens will converge to a point at a distance ' L ' from the common pole P. The value of L is [Refractive index of glass = 1.5 ]

TestHub · Accepted Answer

Lens maker formula: f 1 ​ = ( μ − 1 ) ( R 1 ​ 1 ​ − R 2 ​ 1 ​ ) If incidence ray has direction left to right \& ∣ R 1 ​ ∣ = ∣ R 2 ​ ∣ = 20 cm = R , μ = 1.5 , then ​ f I ​ = ( μ − 1 ) ( R 1 ​ − ( − R ) 1 ​ ) = R 2 ( μ − 1 ) ​ = 20 cm 2 ( 1.5 − 1 ) ​ ⇒ f = 20 cm ​

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