A ray is one of the geometric concepts. Etymology and origin of the word
The words that we use are presented to usfamiliar, familiar from childhood and understandable. It seems to us that we always know what we are talking about and what we mean. But if you try to find out from any passer on the street, for example, the meaning of the word "ray", you can hardly expect a quick and correct answer. Indeed, what is it?
Etymology of the word
Let's look at the beginning with the origin of thisthe words. According to the dictionary of the Russian language, a ray is a stream of light that comes from some source, or a narrow band of light emanating from a glowing object. For example, the rays of the setting sun or the rising sun.
The exact origin of the term is unknown, but,presumably, it originates from the Latin word "light". In Slavic languages this word is found everywhere. In Russian it got their Old Slavonic.
Value and scope
The word "ray" first of all causes associationswith sunlight. How many times everyone has heard the expression: "sunbeams" or "ray of light". But in fact this word has a direct relation to geometry. A ray is a part of a straight line, which is bounded on one side by a point, and on the other by an infinite one.
Any ray has an extreme point. This is the beginning of the ray. Since it does not have an end, it is usually denoted by one letter. In addition, the ray is one of the simplest geometric figures, such as a segment or a broken line.
The concept of a ray is also used in physics, but only in acoustics and geometrical optics. Here the ray is the line along which the light energy moves.
The main feature of the geometric and lightray - this is their straightforwardness. But for light it is true only if it is distributed in a uniform transparent medium. Otherwise it becomes curvilinear.
How to see the light
This experience will be very pleasant for children, it is obviouswill show them what a ray of light is. This requires simple preparations. It is necessary to darken the room and put on the edge of the table any flashlight. A ray of light is now barely visible, but it's only necessary to squeeze a previously prepared plastic bottle with talc or baby powder, like particles of powder, get into it, start to glow. Now children can see that the light ray is a strip of light emanating from a flashlight and continuing into infinity. Why is this happening? The fact is that the light can not be seen until it is reflected from some surface. Particles of talc, hitting a beam of light, make it well visible.