A person wears glasses with a power of -2.5 D . Is the person farsighted or nearsighted, and what is the far point of the person without the glasses?

Step-by-step solution

The power of the lens is given as P = -2.5 D . Since the power is negative, the lens is concave. A concave lens is used to correct nearsightedness (myopia). The focal length of the lens is given by f = 1 P = 1 -2.5 m = -0.4 m = -40 cm . For a nearsighted eye, the corrective lens forms a virtual image of an object at infinity at the person's far point. Using the lens formula 1 v - 1 u = 1 f with u = - , we get v = f = -40 cm . The far point of the person without glasses is 40 cm .