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Defects of vision – myopia
Concepts tested here
- myopia-correction-power
All Questions
2016 Phase II 1 question
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A person can see clearly objects only when they lie between 50 cm and 400 cm from his eyes. In order to increase the maximum distance of distinct vision to infinity, the type and power of the correcting lens, the person has to use, will be:
Concave lens with f equal to the far point distance.
To correct myopia, the far point must go to infinity: v = –4 m, u = –∞.
$P = \frac{1}{f} = \frac{1}{v} - \frac{1}{u} = \frac{1}{-4} - \frac{1}{-\infty} = -0.25$ D
The negative sign implies a concave lens.
