The optician’s prescription for a spectacle lens is marked +0.5D. What is the:
- Nature of spectacle lens?
- Focal length of spectacle lens?
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- Concave lens.
- $\text{P}=+0.5\text{D}$
$\text{f}=\frac{1}{\text{P}}=\frac{1}{0.5}=2\text{m}$
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