The optical power of the lens is -5dopters. Is this lens converging or diffusing? Determine its focal length.

In order to find out what determines the optical power of the lens, we write down the formula for the optical power:

D = 1 / F,

where D is the optical power,
F is the focal length of the lens.

Guided by the written formula, it is easy to understand that if you increase the focal length of the lens, then the optical power of the lens will, on the contrary, increase (inverse proportionality).

We also see that the optical power will be absent when the focal length is equal to 0.

And only when the lens does not focus, but scatters light, the focal length will be negative, due to which the optical power of the lens will also acquire a negative value.