Diameter of plano – convex lens is 6cm and thickness at the centre is 3 mm. If speed of light in material of lens is 2×108m/s, the focal length of the lens is:
A
20 cm
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B
30 cm
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C
10 cm
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D
15 cm
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Solution
The correct option is B 30 cm use trigonometry to find the radius of curvature and once you find the R, use lens maker formula to find the f. Watch the next video for the solution.