A) -2 D
B) + 2 D
C) -0.5 D
D) +0.5 D
Correct Answer: C
Solution :
To correct the myopic defect, concave lens of power - 0.5 D is used as given below. The far point of the myopic eye is 2 metres. Using the lens formula. \[\frac{1}{v}-\frac{1}{u}=\frac{1}{f},\frac{1}{-200}-\frac{1}{\infty }=\frac{1}{f}\] \[\frac{1}{-200}-0=\frac{1}{f}\](because \[\frac{1}{\infty }=0\]) \[-\frac{1}{200}=\frac{1}{f},\] \[f=-200\,cms\] \[P=\frac{1}{f(in\,\,metres)}=\frac{1}{-\,2}=-\,0.5D\]
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