Question.
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem ?
The far point of a myopic person is 80 cm in front of the eye. What is the nature and power of the lens required to correct the problem ?
solution:
For myopia, focal length is given by,
$\mathrm{f}=-\mathrm{x}=-80 \mathrm{~cm}=-\mathbf{0 . 8} \mathrm{m}$
Power, $\mathrm{P}=\frac{1}{\mathrm{f}}=\frac{1}{-0.8}$
$=-1.25$ dioptres.
The lens is a concave lens.
For myopia, focal length is given by,
$\mathrm{f}=-\mathrm{x}=-80 \mathrm{~cm}=-\mathbf{0 . 8} \mathrm{m}$
Power, $\mathrm{P}=\frac{1}{\mathrm{f}}=\frac{1}{-0.8}$
$=-1.25$ dioptres.
The lens is a concave lens.