To construct an image of an object in a lens, it is convenient to use a beam parallel to the main optical axis, a beam passing through the optical center of the lens, and a beam passing through the focus, and then, after refraction, going parallel to the main optical axis
To build an image of a point source located on the main optical one, we conduct the beam at an angle to the axis, then the side optical axis, we find the intersection of the side optical axis with the focal plane of the lens. Pass the refracted beam through this point until it intersects with the main optical axis. This intersection point is a point source image.
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