A lens is a transparent glass body that is bounded by a spherical or cylindrical surface. There are its types: convex and concave.
The structure of glass bodies
Concave (scattering lens) and convex (collective) are composed of wide and thin parts. The scattering lens has a wide part at the edges and a thin one in the center, and a collective lens - on the contrary.
We place such glass bodies in an environment where the refractive index is greater than the refractive index of the above lenses. Then the scattering lens will receive collective properties - and vice versa.
The center of the sphere, part of which is the surface of the body, is called the center of curvature. If one surface is flat, then they say that it is in infinity.
A straight line connecting the centers of curvature of surfaces that have a spherical shape is defined as the main optical axis. It is perpendicular to the surface of the lens at the points through which it passes. The point lying on the optical axis in the center is the optical center. Any straight line that can pass through such a center at a right angle to the main axis is considered to be secondary.
The point where all the rays are collected, which, in turn, go parallel to the optical axis after exiting the lens, is called the focus. And the point where the extensions of the rays that are scattered are collected is called the imaginary focus of the scattering lens.
The distance from the center (meaning the optical center) to the focus of the glass body is the focal length. The plane that is drawn through the points in focus and, in turn, passes perpendicular to the optical axis, is called focal.
In order to complete the construction of the image in the scattering lens of some object, which gives the lens, it is necessary to build an image of its extreme points. It should be remembered that the rays that fall on the glass body will be parallel to the main optical axis when they come out and pass through the focus. And the rays that incident on the lens through the focus, after the exit will go parallel to the beam. If the beam hits the optical center, then after exiting it, it will move in the same direction, that is, it will not be refracted.
If we denote the distance from the subject to the lens by b, and the distance from the image to the lens by v, with the focal length marked V, then the following equality holds:
1 / b + 1 / v = 1 / V.
Such an equation is considered the lens formula. It is necessary to determine the distance to the image with different placement of the object relative to the glass body.
If such a distance ultimately comes out negative, then this indicates that the image of the subject is on the same side of the lens as the subject. Therefore, if it is a scattering lens, the focal length in the last formula must be taken with a minus sign, since a negative value cannot be avoided.
A value that is inverse to the focal length is considered optical power. It is measured in diopters. Knowing the size of the image that the lens gives and the size of the subject, you can determine the linear magnification that the glass body gives. Such an increase equals the ratio of the height of the image to the height of the subject itself.
Scattering lens. Image building
The subject is in infinity. Then the image of such an object will be in imaginary focus. Its dimensions and parameters can only be assumed, since the exact value cannot be achieved.
The subject is a short distance from the glass body. For a scattering lens, wherever the subject is located, its image will always be on the same side of the lens as the subject itself. The image will be reduced, imaginary and direct.