البصريات الهندسية - الضوء .. الفيزياء

Geometric Optics - Light .. Physics

Geometric Optics

Curved lenses or mirrors with specific shapes are used to refract light and send it in the required directions. A convex lens (curved outward) or a concave mirror (curved inward) can collect parallel rays at a single point called the focus. Concave lenses or convex mirrors disperse the rays so that they appear to be emanating from the same focus.

The greater the curvature of the surface of the lens or mirror, the closer the focus is to the lens.

When the rays coming from an illuminated or reflective body fall on a lens or mirror, an image of the body itself is formed as a result. The mirror reflects the light according to the laws of reflection. If it falls perpendicular to it, it returns in the same direction. As for the penetration of light into the lens, it is subject to the laws of refraction of light.

It is known that light is not refracted if it passes through the center of the lens. All these rules help to determine the final image of the body geometrically because it is a meeting point for all these rays.

The image of the body is real if it can be focused focally on a specific curtain. In some cases where the body occupies specific positions according to the center of focus, the rays disperse after being reflected or refracted and appear as if they are emanating from the image itself, which in this case is called a virtual image (like the image formed by a flat mirror). In some cases, the image emanating from a mirror or lens is inverted, meaning that its top is down and its bottom is up.

It is known that the light that falls on the eye is refracted twice: once in the pupil and once in the cornea, then it is focused focally on a sensitive part of the retina called the concavity. The retina contains two types of cells that are very sensitive to light: cone cells, which are concentrated in the crater, and rod cells, whose job is to send pulses to the brain via the fibers of the optic nerve itself.

The ciliary muscles, which are connected to the pupil by specific ligaments, control the eye's ability to collect light inside it. As for the pupil, its job is to control the amount of light entering it, through its ability to change the length of its diameter.

Therefore, it expands at night and narrows during the day.

Images are formed using lenses and mirrors (to the left).