1.1 human eyes with convex lens
Schematic diagram of human eye imaging is the image formed by human eyes a real image or an imaginary image? We know that the structure of the human eye is equivalent to a convex lens, so the image of external objects on the retina must be a real image. According to the above empirical law, the image on the retina seems to be inverted. But any object we usually see is upright? This problem that conflicts with experience and law actually involves the adjustment of cerebral cortex and the influence of life experience. Due to visual errors, the human eye believes that light is emitted by objects and directly into the human eye.
When the distance between the object and the convex lens is greater than the focal length of the lens, the object becomes an inverted image. When the object approaches the lens from a distance, the image becomes larger and the distance from the image to the lens becomes larger; When the distance between the object and the lens is less than the focal length, the object becomes an enlarged image. This image is not the convergence point of the actual refracted light, but the intersection of their reverse extension lines. It can not be received by the light screen. It is a virtual image. Virtual image contrast formed by plane mirror (can’t be received by light screen, can only be seen by eyes).
1.2 camera with convex lens
The lens of a camera is a convex lens. The scene to be photographed is an object, and the film is the screen. The light irradiated on the object is diffusely reflected, and the image of the object is formed on the final film through a convex lens; The film is coated with a layer of light sensitive material, which changes chemically after exposure, and the image of the object is recorded on the film. The relationship between object distance and image distance is exactly the same as that of convex lens. When the object approaches, the image becomes farther and farther away and larger, and finally forms a virtual image on the same side. When the object distance increases, the image distance decreases and the image becomes smaller; As the object distance decreases, the image distance increases and the image becomes larger. One focal length is divided into virtual and real, and two focal lengths are divided into size.
1.3 others with convex lens
Projector, slide projector, projector, magnifying glass, searchlight, camera and camera all use convex lens, which improves our life and is used in life all the time. Hyperopia glasses are convex lenses, and myopia glasses are concave lenses.
In addition, the convex lens is also used to:
(1) Shooting and video recording;
(2) Projection, slide, movie;
(3) For special effect lighting (focusing into various colors);
(4) Virtual image is used to enlarge words, artifacts, maps, etc.
As can be seen from the above, the application of convex lens in our life can be said to be various. Students who are good at discovering can also find out more about the use of convex lens imaging in life.
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