There are several immigrant villages in Roy.

For a convex lens, there is a focus on the left and right sides. These two focuses are the real focus. The actual light is convergent.

For a concave lens, there is a focus on the left and right sides. Both focus points are virtual focus points. It is not composed of actual light.

A convex lens is made according to the refraction principle of light. A convex lens is a lens with a thick center and a thin edge. Convex lenses are divided into biconvex, plano-convex, concave-convex (or positive meniscus) and other forms. Convex lens is also called convergent lens, because it can converge light, while thicker convex lens has telescopic and convergent functions, which is related to the thickness of the lens. Hyperopia glasses are convex lenses.

Extended data:

The imaging law of convex lens is: when the object distance is less than a focal length, an upright and enlarged virtual image is obtained; When the focal length is between 1-2 times, the inverted magnified real image is obtained; Beyond the double focal length, the real image is reversed and reduced.

The geometric drawing of concave lens imaging is the same as that of convex lens. From the top of the object, it is also regarded as two straight lines: one parallel to the main optical axis, deflected into divergent light after passing through the concave lens, and returned 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, which is the image of the object.

The camera adopts the imaging law of convex lens. The lens is a convex lens, the scene to be shot is an object, and the film is a screen. The light shining on the object is diffusely reflected and imaged on the final film through the convex lens. The film is coated with a layer of photosensitive substance, which changes chemically after exposure, and the image of the object is recorded on the film.

As for the relationship between object distance and image distance, it is exactly the same as the imaging law of convex lens. When the object approaches, the image gets farther and bigger, and finally becomes a virtual image on the same side.

When the object is a virtual object and the distance from the concave lens to the virtual object is twice the focal length (absolute value u=2f), it becomes a virtual image with the same size as the object, and the image and the object are on the opposite side of the lens; When the object is a virtual object, the distance from the concave lens to the virtual object is greater than twice the focal length (referring to the absolute value u >；; 2f), it becomes an inverted and reduced virtual image, with images and objects on the opposite side of the lens.

Baidu encyclopedia-convex lens

Baidu encyclopedia-concave lens