Question

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

Answer 1

Answer:

Power of lens= 1/focal length

⇒ focal length = 1/power of lens

=1/1.5

=0.6667 m

Since the focal length is positive, the prescribed lens is convex and is converging lens.

Answer 2

Answer:

$The \: power \: of \: this \: lens \: is \: positive , \\ therfore, \: this \: is \: a \: convex \: lens \: or \: \\ converging \: lens. \: now, \\ Power, p = \frac{1}{f(in \: metrs)} \\ so \: \: \: \: \: + 1.5 = \frac{1}{f} \\ or \: \: \: f = \frac{1}{ + 1.5} \: m \\ f = + \frac{1}{1.5} \times 100cm \\ \\ So, \: \: \: focal \: length \: of \: lens \: f = + \: 66.7cm$