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lens and image

- Eye of the camera
The camera is very similar to the human eye, and picture (1) shows a simplified section of that eye, where we see the lens that, parallel to the lens in the camera, has an iris diaphragm that parallels the diaphragme in the camera.

The lens in the eye projects a clear image onto the retina, and its light causes physical and chemical changes on it, which the optic nerve transmits to the brain in the form of a message, just as the lens in the camera projects an image onto a film coated with a light-sensitive substance, and then chemical reactions and transformations occur in that substance that can be endorsed to different degrees. Grays form an image.
In a way, the lens can be said to be the eye of the camera.

Let's restore the experiment that we explained in the previous episode, whereby we dropped a picture of a lamp or a window by means of a regular magnifying glass on a reinforced piece of paper, and let's continue the experiment.

Hold the lens between the light source and the cardboard, and after obtaining a clear projected image on the paper, keep the lens and paper steady, and get close to the window or the distance between the lamp. So what happens?

We notice that the image projected on the paper increases in size, but it loses its clarity and becomes cloudy. In order to get a clear image again, the lens must be moved a little away from the paper.
The relationship between these dimensions, or distances, is a fixed relationship, in the sense that for every distance of the subject, or the light source, from the lens, there is a certain distance, between the lens and the paper, or the “focusing surface” in which we get a clear picture of that, and to get Projecting a clear image on the film in the camera, it must be possible to make the focus or what it means possible to move the lens far or near, to the appropriate position, in relation to the distance of the subject to be photographed. .



Now let's see how the lenses work.
When a beam of light passes through a transparent material to another transparent material of different density, its path is refracted at the point where the two materials meet, and this property is
that enables the lens to form an image.
(Fig. 2)

This drawing shows a magnifying glass, like the one used in reading, and to its left is a lit object that reflects light in all directions.

Let us take a single ray of light reflected from point (H) (on the subject), and suppose that this ray falls on the lens at point (A), when it penetrates the lens (a transparent material whose density is different from the density of air), this ray is refracted downward, and refracted once. A second downward as well when it comes out into the air.
Let us now take another ray reflected at point (H) itself, and it falls on the lens at point (B). This breaks twice, once when it enters the lens, and once when it leaves it, at slightly different angles. For the angles of refraction at point (A). The two rays meet at point (h), as shown in the figure. We notice that another ray reflected at point (H) and penetrating the lens at point (C) is refracted twice and meets the previous rays at the same point (h).

This example illustrates the importance of the curvature of the lens surfaces. This curvature makes it a focus where all the rays reflected from a point on a specific object, and refracted at any point on the surface of the lens, meet. f) on the opposite side of the subject in relation to the lens.
As we notice, the image projected through the lens is an inverted image.