Concave lens is also called negative spherical lens. The middle of the lens is thin, the edge is thick and concave, so it is also called concave lens. Concave lenses have a divergent effect on light.
The principle is that the top of the object is also regarded as two straight lines: one is parallel to the main optical axis, deflected into divergent light after passing through the concave lens, and returns the refracted light to the main focus in the opposite direction; The other line passes through the optical center of the lens, and these two straight lines intersect at one point.
Extended data:
Concave lenses are divided into biconcave lenses, plano-concave lenses and convex-concave lenses. The line connecting the curvature centers on both sides is called the principal axis, and the center point O is the optical center.
The light passing through the optical center will not be refracted no matter where it comes from. The light beam parallel to the principal axis is refracted on the concave lens and then diverges in all directions, and the extension line opposite to its divergence direction will all be at point F on the same side as the light source, and its refracted light will just emanate from point F, which is called virtual focus. One on each side of the lens.
Therefore, the image formed by concave lens is always smaller than the vertical virtual image of the object, and concave lens is mainly used to correct myopia.
Myopia is mainly due to lens deformation, which leads to premature light gathering in front of the retina. The concave lens plays the role of diverging light. The concave lens forms an upright and reduced virtual image, which lengthens the image distance and falls right on the retina.
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