When the lens is imaged, all the light emitted by each point on the object is imaged in the same position, which blocks a part and does not affect the imaging of other light emitted to the lens, so the complete image can still be seen, but the brightness of the image on the screen will be darkened due to the decrease of light emitted to the image.
Widely used in security, car wear, digital cameras, lasers, optical instruments and other fields. Various common colorless optical glasses include melting time, calcium fluoride, magnesium fluoride, silicon, germanium, zinc selenide and other materials; As well as plano-convex lens, biconvex lens, plano-concave lens, biconcave lens, super-hemispherical lens, small ball lens, meniscus lens, cylindrical lens, rod lens, cemented lens and so on.
Lenses are optical elements made of transparent substances (such as glass and crystal). A lens is a refracting mirror, and its refracting surface is the transparent body of two spheres (a part of a sphere) or a sphere (a part of a sphere) and a plane. Its image is both real and virtual. Lenses can generally be divided into two categories: convex lenses and concave lenses. The central part is thicker than the edge part, which is called convex lens, including biconvex, plano-convex and concave-convex. The central part is thinner than the edge part, which is called concave lens. There are three types: double concave, flat concave and convex concave.
In physics, lenses are imaged according to the refraction principle of light, and optical microscopes and telescopes are made according to the refraction and linear propagation principle of light.
Imaging features: first put the object away from the lens to see the position and size of the image, then move the object to the convex lens, and then see the change of the size and position of the image. (1) Things are far away, like being born in the focus, like being very small.
(2) When the object moves in front of the convex lens, the image moves out of the convex lens from the focus, and the image becomes larger and inverted.
(3) When the object is not far from the focus, it looks far away and looks big.
(4) When the object is in focus, no image can be found and no image is formed.
(5) The object can't get an image at the focal point, but the eye can see an enlarged vertical virtual image through the lens.
The imaging principle of convex lens and concave lens is based on the different refractive index of different transparent media, and the incident angle and refraction angle of light from one media are not equal, thus producing different images.