# 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 Ritesh|Updated : November 7th, 2022

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.

### 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:

## 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?

A +1.5D power corrective lens has been recommended by a doctor. The lens has a 0.67 m focal length. The converging lens that is being prescribed. In a converging lens, the focal length is positive.