A patient with a lens-to-retina distance of 2.5 cm and a lens strength of 45 D can clearly see an object.  What is the distance from the patient's eye to the object?A.0.2 mB.0.3 mC.1 mD.5 m

The lens formula is 1/f = 1/v - 1/u, where f is the focal length of the lens, v is the image distance (lens to retina), and u is the object distance (distance from the patient's eye to the object).

Given that the lens strength (power) is 45 D (diopters), we can find the focal length of the lens. The power of a lens is the reciprocal of its focal length (in meters). So, f = 1/P = 1/45 = 0.0222 m or 2.22 cm.

The lens-to-retina distance is given as 2.5 cm. In a healthy eye, the image is formed on the retina, so the image distance v = 2.5 cm = 0.025 m.

Substituting these values into the lens formula:

1/0.0222 = 1/0.025 - 1/u

Solving for u gives u = -0.1 m.

The negative sign indicates that the object is on the same side of the lens as the light that is coming in, which is the usual situation for a lens in an eye. However, distances are usually given as positive, so the distance from the patient's eye to the object is 0.1 m.

So, none of the options A, B, C, D are correct. The correct answer should be 0.1 m.