Question

A doctor has prescribed a corrective lens of power +1.5D. Find the focal length of the lens. Is the prescribed lens diverging converging

Answer 1

Given: P = 1.5D

Find : F = ?

Solution : Focal length = 1÷P

= 1 ÷ 1.5

F = 0.6666.....

F = 0.67

Therefore , lens is convex

And It is converging lens.

Hope you get it !!!!

Answer 2

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the power of this lens is positive, therefore,

this is a convex lens or converging lens now

$power \:( p) \: = \frac{1}{f(in \: metres)}$

$so \: \: + 1.5 = \frac{1}{f}$

$or \: \: f \: = \frac{1}{ + 1.5} m$

$\implies \: f = + \frac{1}{1.5} \times 100cm$

$so, \: Focal \: length \: of \: lens \: (f) = + 66.7cm$