What is a convex lens?
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A lens (from the Latin for "lentil seed," which has the characteristic thick in the middle and thin at the edges shape) is any piece of glass or other transparent material with at least one curved surface. A convex lens is a class of lens that causes light passing through it to converge, as opposed to the class of concave lenses, which cause light passing through them to diverge. Where the light converges after passing through a convex lens is termed the focus; the distance between the focus and the center of the lens itself is called the focal length. The shorter the focal length on a convex lens, the more drastically the light is bent to meet at the focus, and the more powerful the lens.
Understanding Physics, I. Asimov, pg 31, Barnes & Noble, 1966.
The lens with a curved shape is named a convex lens; in fact, a convex lens has a bulky center and thin edges. A convex lens inverts the image and it's used to bring a small image closer. That's why convex lenses are often used as magnifying glasses--because of their property to make things look bigger.
A Convex lens converges a beam of light i.e. the rays of light all meet or converge at a point.
Main features of convex lens include:
- The optical center-the point midway between the lens surface on the principal axis.
- Principal axis-line passing symmetrically through the optical center of the lens.
- Focal point F-the point on the principal axis to which all rays parallel to the principal axis converge to, after refraction.
- Focal length f-distance between optical center and focal point.
- The focal plane-plane which passes through F and P. The focal plane is perpendicular to the principal axis.
The simplest example of a convex lens is a magnifying glass.
A convex lens is also known as a converging lens. A converging lens is a lens that converges rays of light that are traveling parallel to its principal axis. They can be identified by their shape which is relatively thick across the middle and thin at the upper and lower edges.
A convex lens is a converging lens. When parallel rays of light pass through a convex lens the refracted rays converge at one point called the principal focus. The distance between the principal focus and the centre of the lens is called the focal length.
A concave lens is a lens that possesses at least one surface that curves inwards. It is a diverginglens, meaning that it spreads out light rays that have been refracted through it. A concave lens is thinner at its centre than at its edges, and is used to correct short-sightedness (myopia).
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