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Determine the focal length of the lens made up of a material of refractive index 1.52 as shown in the diagram. ( PointsC_(1) and C_(2) are the centers of curvature of the first and second surface). |
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Answer» Solution :This lens is called convexo - concave lens Give: `n = 1.52, R_(1) = 10 CM and R_(2) = 20` Lens makers formula. `(1)/(F) = (n-1)((1)/(R_(1))-(1)/(R_(2)))` Substituting the values. `(1)/(f)=(1.52-1)((1)/(10)-(1)/(20))` `(1)/(f)=(0.52)((2-1)/(20))=(0.52)((1)/(20))=(0.52)/(20)` `f = (20)/(0.52) = 38.46 cm` 
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