Question

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

Answer 1

 Power of a lens is given by:  

 Power (P) =`1/f` 

`f=1/f` 

⇒`f=1/-1.5` 

∴ f=-66.67 cm 

Since the power is negative, the lens is of a diverging nature. Therefore, it's a concave lens.