What is Lenses and Light? | Definition, Types, Formula & Examples

What is Lenses and Light?

A lens is a curved piece of glass or plastic designed to refract light in a specific way. Lenses are used in eyeglasses and contact lenses to help correct vision. They are used in telescopes to help see distant objects and in microscopes to help see very small objects.

Refraction

When a light wave travels from one medium, (such as air) to another (such as glass), the light ray is bent. This is called refraction. By using refraction, lenses can bend many light rays. Most of the lenses we use in everyday life are designed to deflect light rays to a specific focal point where elements will be in focus (obviously).

Types of Lenses

There are different ways to classify lenses. One way to classify lenses is how they deflect light.

Converging

A converging lens causes light rays to be bent towards a specific focus. Another name for this type of lens is positive lens.

Diverging

A diverging lens will cause light rays from a definite focal point to be scattered. Another name for this type of lens is a negative lens.

Other Types of Lenses

Another way to classify lenses is by the curve of the glass on either side of the lens. There are terms used to describe each party. Then the two sides are combined to come up with the name of the target.

Convex – A convex lens is a lens whose center is thicker than its edges.

Concave – A concave lens is a lens whose center is thinner than its edges. One way to remember the difference between two lenses is to think of “collapse” with concave lenses.

Plano – A plano lens is a planar lens. This is used when one is flat and the other is concave or convex. The apartment can be considered as a “plain”.

Meniscus – A meniscus lens is a lens with one concave and one convex side.

Putting the Names Together

Biconvex – A lens with both convex faces is biconvex. A biconvex lens is a converging lens.

Plano-convex – A lens in which one side is convex and the other is plane. Plane-convex lenses are converging lenses.

Biconcave – A lens with both concave sides is two concave faces. A biconcave lens is a diverging lens.

Plano-concave – A lens in which one side is concave and the other is flat. Plane-concave lenses are diverging lenses.

Positive meniscus – A converging lens has one side concave and the other convex.

Negative meniscus – A diverging lens has one concave and one convex facet.

Focal Point

The focal point of a lens is usually denoted by a capital “F”. A point in space where light rays, after passing through a converging lens, will converge towards that point. A diverging lens will have a negative focal point where the rays originate before diverging through the lens.

Focal Length

The focal length is the distance from the center of the lens to the focal point.

Principal Axis

The principal axis is an imaginary horizontal line passing through the center of the lens. In a perfect lens, the focal point will be on the principal axis at a distance equal to the focal length from the center of the lens.