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प्रश्न
A doctor has prescribed a corrective lens of power, −1.5 D. Find the focal length of the lens. Is the prescribed lens diverging or converging?
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उत्तर
Power of a lens is given by:
Power (P) =`1/f`
`f=1/f`
⇒`f=1/-1.5`
∴ f=-66.67 cm
Since the power is negative, the lens is of a diverging nature. Therefore, it's a concave lens.
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