The optical power of the lens is 4 diopters. What kind of lens is it? Determine its focal length.

Let’s give a slightly more detailed answer to your question. When D> 0, then the lens is converging. If, according to the condition of the problem, the value of D is expressed by a number that is less than 1, then without hesitation – the lens is scattering. Let’s get back to the problem. The first question was answered: the lens is collecting. Find the focus: D = 1 / F; express F, F = 1 / D = 1/4 = 0.25 (m).