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Question
If AB = 10 cm & DB = 40 cm (diameter). What is the radius of curvature & focal length?
If AB = 10 cm & DB = 40 cm (diameter). What is the radius of curvature & focal length?
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Solution
The correct option is D 20 cm, 10 cm
Since the diameter is equal to 40 cm then the radius of curvature is equal to half of it. Centre of curvature = radius of curvature = 20 cm. The focus is point A since parallel rays pass through point A. So, AB = focal length = 10 cm.
20 cm, 10 cm
Since the diameter is equal to 40 cm then the radius of curvature is equal to half of it. Centre of curvature = radius of curvature = 20 cm. The focus is point A since parallel rays pass through point A. So, AB = focal length = 10 cm.
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