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

By BYJU'S Exam Prep

Updated on: September 25th, 2023

A doctor has prescribed a corrective lens of +1.5D power. The focal length of the lens is 0.67 m. The prescribed lens is a converging lens. Steps to Calculate the Focal Length of Lens.

Step 1: It is given that the patient’s doctor has recommended a corrective lens with the power of:

P = +1.5D

Step 2: To calculate focal length, we can use the formula:

f = 1/P [where f = focal length, P = power]

Step 3: Now we have to calculate the focal length:

Substitute P in the above formula we get

f = 1/P

On substituting we get

f = 1/+1.5

f = 0.67 m

The focal length of the lens is 0.67m.

Table of content

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

Focal Length of Lens

The corrective lens has a good focal length. The converging lens has a positive focal length. Thus, the converging lens that the doctor has recommended will correct vision problems.

The focal length of a mirror (or lens) is the separation between its pole and focal point. It can also be measured as the distance between its optical center and pole.
The point at which a parallel beam of light is focused after reflection in the mirror is known as the focal point (F) of a mirror.
For a convex lens and convex mirror, the focal length is assumed to be positive.
For a concave lens and a concave mirror, it is regarded negatively.
It is denoted by f. Here, PF = f

Therefore, the patient’s prescription corrective lens has a focal length of +0.67m. The doctor has recommended a converging lens as a corrective lens.

Summary: