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प्रश्न
The optician's prescription for a spectacle lens is marked +0.5 D. What is the:
(a) nature of spectacle lens?
(b) focal length of spectacle lens?
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उत्तर
Positive power indicates it is a converging lens.
Power of a lens is given by:
power(p)=`1/f`
`0.5=1/f`
`f=1/0.5`
`f=2m`
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