The use of concave lenses, the characteristics of concave lenses

There are three types of lenses: double-concave, plano-concave and convex and concave. The line connecting the center of curvature of the two sides is called the main axis, and the point o of its ** is called the optical center. Light passing through the center of light is not refracted, no matter where it comes from.

The beam of light with parallel principal axis is refracted on the concave lens and diverges in all directions, and the extension line against its divergence direction will be at a point f on the same side as the light source, and the refracted light will be emitted from point f, which is called the imaginary focus. One on each side of the lens. Concave lenses are also known as divergent lenses.

The focal length of a concave lens is the distance from the focal point to the center of the lens. The larger the radius of the lens, the longer the focal length, and in the case of a thin lens, the focal lengths on both sides are equal.

Both sides are spherical or one side is spherical and the other side is a flat transparent body, and the middle part is thinner, which is called a concave lens. When used in an optophobic medium, it can diverge the incident beam, so it is also called a divergent lens. It is also known as a negative lens because of its negative focal length.

For thin concave lenses, the imaging formula, lateral magnification formula, and symbol rule are the same as those of convex lenses.

The image formed by the concave lens is always smaller than the upright virtual image of the object, and the concave lens is mainly used to correct myopia. Myopia is mainly due to the deformation of the lens, which causes the light rays to converge in front of the retina prematurely. The concave lens plays the role of diverging light, and the concave lens becomes an upright, shrinking virtual image, so that the image distance becomes longer, which happens to fall on the retina.

Concave lenses are also known as negative ball lenses, and the middle of the lens is thin, the edges are thick, and they are concave, so they are also called concave lenses. Concave lenses have a divergent effect on light. Myopia glasses are concave lenses.

Concave lenses are divided into double concave, plano-concave, and convex and concave (Note: convex and concave lenses are concave and concave are concave and convex lenses are convex and convex!). and so on.

After the parallel rays are deflected through the concave spherical lens, the rays diverge and become divergent rays, and it is impossible to form a solid focus, and along the reverse extension line of the scattered rays, they intersect at point f on the same side of the projected rays, forming a virtual focus. (Concave lenses have two imaginary focal points).

The geometric mapping of concave lens imaging is the same as that of convex lenses. From the top of the object, it also acts as two straight lines: one is parallel to the main optical axis, which is deflected into divergent light after passing through a concave lens, and the refracted light is returned to the main focus in the opposite direction; The other is the image of the object through the optical center point of the lens, where the two straight lines intersect at one point.

Through the concave lens, the image is reduced by being upright and upright, and the object and the image are on the same side of the lens.

When the object is a physical object, it becomes an upright and shrunken virtual image, and the image and the object are on the same side of the lens; When the object is a virtual object, and the distance between the concave lens and the virtual object is one time the focal length (referring to the absolute value U2F), it becomes an inverted and reduced virtual image, and the image and the object are on the opposite side of the lens.

Concave lens, which has a divergent effect on light. The reverse extension of the divergent light will meet a point on the side of the concave lens, which is called the "focus" of the concave lens, denoted by "f"; The focal point of the concave lens is a virtual focus, one on the left and one on the left and one on the left, and there are two virtual focal points in total; The distance from the focal point to the center of light o is called the "focal length" of the concave lens, which is denoted by "f".

Convex lens: It has a converging effect on light rays. The point at which the rays converge and intersect on the side of the convex lens, this point is called the "focus" of the convex lens, which is denoted by "f"; The focal point of the convex lens is a solid focus, one on each side, and there are two real focal points in total; The distance from the focal point to the optical center o is called the "focal length" of the convex lens and is denoted by "f".