Lens: A lens is an optical element whose surface is a part of a spherical surface made of transparent material.
The optical center of the lens:
As shown in the figure above, the geometric center O of the lens is generally called the optical center of the lens.
The main optical axis of the lens:
As shown in the figure above, a horizontal straight line passing through the optical center of the lens is called the main optical axis of the lens.
The focal point of the lens:
Take a convex lens as an example. As shown in the figure above, because the lens has a converging effect on light, a beam of light parallel to the main optical axis (parallel light) will converge at a point after passing through the convex lens. This point is called the focal point of the lens and is represented by a capital letter F. Said.
The focal length of the lens:
A measure of the concentration or divergence of light in an optical system, which refers to the distance from the optical center of the lens to the focal point of the light when parallel light is incident. An optical system with a short focal length has a better ability to gather light than an optical system with a long focal length. Simply put, the focal length is the distance between the focal point and the center point of the mirror. That is, the focal length is the distance from the focal point to the optical center of the lens, which is represented by a lowercase letter f. As shown in FIG.
Convex lens:
A lens with thin edges and thick middle and at least one surface is made of a spherical surface. The several types shown in the figure below can all be called convex lenses. The convex lens has a condensing effect on light.
Concave lens:
The edge is thick, the middle is thin, and at least one surface is made into a spherical lens. The several types shown in the figure above can all be called concave lenses. The concave lens has a divergent effect on light.
