Simplistic assumptions of geometric optics include that light rays: A ray of light is a line (straight or curved) perpendicular to the wavefronts of light; Its tangent is collinear with the wave vector. Light rays in homogeneous media are straight. They bend at the interface between two different media and can be bent in a medium in which the refractive index changes. Geometric optics describes how rays propagate through an optical system. The objects to be imaged are treated as collections of independent point sources, each producing spherical wavefronts and corresponding outer beams. The rays of any object point can be propagated mathematically to locate the corresponding point on the image. The light from one of the light sources goes in all directions and moves in a straight line. When it hits an object, it scatters from any point in all directions. Some of these rays enter our eyes and allow us to see the object. We can conclude that the light is scattered in all directions, because many people in different places can see the same point.

We have a lot of experience with light. One of the first tasks of a newborn is to learn how to interpret the light his eyes receive and break down the world into objects. We live with light every day and interpret it naturally, automatically and without thinking about it. But understanding what is happening and what light is is not so trivial. The ray model is very useful for studying light reflection, light refraction, and various images produced by lenses, spherical mirrors, and planar mirrors. A nice demonstration of the brain interpreting signals from sight, rather than just „seeing” them directly, is Ed Adelson`s Checkershadow demonstration on the right. Surprisingly, the two squares labeled A and B have the same shade of gray. Check it yourself by printing and cutting it or using a clipping program to trim the images of the two squares on your screen and place them next to each other.

Some computers have a digital colorimeter that allows you to read color details for every pixel on your screen. (On a Mac, look for DigitalColorMeter under Applications/Utilities.) The brain doesn`t really make a mistake here; It interprets the information according to the context. If two regions are the same color and one is in the light and the other in the shadow, then „really” (if displayed in the same light) those in the shadow will be brighter – and your brain handles that and shows it to you automatically. He proposed the idea that light is made up of small particles that move very, very fast. As a result, they seemed to move in a straight line. Although gravity would let them down, it would be a tiny and negligible effect. (Due to the high speed of light, it wouldn`t have time to fall very far.) The reflection simply came out assuming elastic bounce and no friction on the surface, so that the velocity component remained the same parallel to the surface and the perpendicular to it was reversed only by the inversion. To obtain Snell`s law, which maintains the idea that there is no friction at the surface so that the parallel to the surface component of the velocity does not change, he had to assume that the light particle became faster in the denser medium.

As the velocity component became longer perpendicular to the surface, it bent the velocity vector in the direction of normals – as observed. From our experience with light, dark and shadow, we can draw some basic ideas: There are many special rays used in optical modeling to analyze an optical system. These are defined and described below, grouped according to the type of system for which they are used. If the reflection takes place from a perfectly flat surface, we call it regular reflection. Reflected light has greater intensity in one direction and negligible intensity in all other directions. To find out what our experiment tells us about light, let`s start with the basic assumption: when reflection takes place from an irregular or rough surface, the regular characteristic of light is not observed, and although the light beam is reflected at all points, the overall observed effect is essentially the cancellation and overlapping of all reflected rays, resulting in diffuse reflection. Newton was not satisfied with these basic principles, most of which were already known when he began to think about light as a young man when he fled London during the plague. (He discovered the principle of color.) He was always interested in mechanisms – what things were – and mathematization – what mathematical rules they followed; And of course, how did it all fit together? The light beam model consists of several components that help you understand a diagram.

An interesting experiment is to direct a laser beam at a wall. The spot is visible, but the beam (beam) from the laser to the wall is not, unless you scatter dust in its path! A beam of light is reflected from a smooth surface in such a way that the incident angle beam becomes normal at the point of incidence of the reflecting surface, which corresponds exactly to the angle that the reflected beam makes relative to normal. In addition, the beam reflected with the incident beam and the perpendicular to the reflecting surface are all on the same plane defined at the point of incidence, and it shows θi = θr. In physics, ray tracing is a method of calculating the path of waves or particles through a system with regions of different propagation velocities, absorption properties, and reflective surfaces. Under these circumstances, wavefronts can bend, change direction or be reflected on surfaces, making analysis difficult.

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