A) \[~+\,2D\]
B) \[~+\text{ }0.50\,D\]
C) \[-2D\]
D) \[-0.5D\]
Correct Answer: D
Solution :
Distance of vision \[\mu =2\,m\] As the man is unable to see distinctly beyond 2 m. Hence, all the objects placed beyond 2 m (i.e.,\[u=\infty \]) must form an image at a distance less or equal to 2 m. The relation for focal length of a lens is \[\frac{1}{f}=\frac{1}{\upsilon }-\frac{1}{u}=\frac{1}{\infty }-\frac{1}{2}=-\frac{1}{2}\]or \[f=-2m\] Hence, the required power of a lens.
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