Question

What is the power of a concave lens?
A. Positive
B. Negative
C. Neutral
D. None

Answer 1

Hint:In order to answer this question, first we will mention the sign of the power of concave lenses. And then we will explain the power of a concave lens and why its power has a particular sign.

Complete answer:
The power of the concave lens is negative. Concave lens surfaces have a virtual radius of curvature, and thus a negative curvature. Optical power is denoted by the same convention signs that are used for focal length. Convex lenses have a positive focal length and optical power because they have a genuine focus.

Concave lenses have a negative focal length and optical power because they have a virtual focus. The reciprocal of the focal length is the lens's power. As a diverging lens, a concave lens will always have a negative focal length. As a result, the power of a concave lens is negative as well.A lens's power is expressed as \[P = 1F\] , where f is the focal length.

The ${m^{ - 1}}$ is the S.I. unit of lens power. This is also referred to as diopter. A converging lens' focal length $(f)$ is positive, while a diverging lens' focal length $(f)$ is negative. A virtual image is produced at the focus when an object is positioned at infinity. When compared to the size of the thing, the image is significantly smaller. A virtual picture is produced between the pole and focus of the convex lens when an object is positioned at a finite distance from the lens.

Hence, the correct option is B.

Note:A concave lens is used to pass light through. As you can see, as the light travels through the lens, it spreads out or diverges. Concave lenses, while less frequent than convex lenses, have a variety of applications. Nearsightedness is a condition that is treated with concave lenses (also called myopia).