Question

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

Answer 1

Answer:

f=0.66m or 66cm

Explanation:

D=1/f

f=1/D

f= 1/+1.5=+0.66m or +66cm

As the focal length is positive

the lens is converging or convex

Answer 2

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the power of this lens is positive, therefore,

this is a convex lens or converging lens now

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

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

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

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

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