Concave lens is used to correct

The principle of geometric drawing of biconcave lens imaging is the same as that of convex lens. The top of the object is also regarded as two straight lines: one is parallel to the main optical axis, deflects into divergent light after passing through the biconcave lens, and returns the refracted light to the main focus in the opposite direction; The other passes through the optical center point of the lens. The two straight lines intersect at one point, which is the image of the object.

The line connecting the centers of curvature on both sides is called the principal axis, and the central point O is called the optical center. Light passing through the optical center does not refract no matter where it comes from. The beam parallel to the main axis refracts on the concave lens and diverges to the four directions. The extension line against its divergence direction will all be at a point F on the same side as the light source, and its refracted light will just be emitted from point F, which is called the virtual focus. One on each side of the lens. Biconcave lens is also called divergent lens. The focal length of a concave lens refers to the distance from the focal point to the center of the lens. The larger the radius of the lens, the longer the focal length. If it is a thin lens, the focal lengths on both sides are equal.

When used in light sparse medium, it can diverge the incident beam, so it is also called divergent lens. It is also called negative lens because its focal length is negative. For thin concave lens, the imaging formula, transverse magnification formula and sign rule are the same as those for convex lens.

The image formed by biconcave lens is always smaller than the vertical virtual image of the object. Biconcave lens is mainly used to correct myopia. Myopia is mainly due to the deformation of the lens, resulting in the premature collection of light in front of the retina. The biconcave lens plays the role of divergent light. The biconcave lens becomes an upright and reduced virtual image, which lengthens the image distance and just falls on the retina.

Lens is a kind of refractive optical element made of different optical materials. Its refractive surface is two spheres or one sphere. According to its shape, it can be divided into convex lens (positive lens) and concave lens (negative lens). The lens whose central part is thicker than the edge is called convex lens. According to their cross-sectional shape, there are biconvex lens, flat convex lens and concave convex lens. The lens whose central part is thinner than the edge is called concave lens. According to its different cross-sectional shape, it can be divided into double concave lens, flat concave lens and convex concave lens.