The words that we use seem familiar to us, 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 passerby on the street, for example, the meaning of the word "ray", you can hardly count on a quick and correct answer. Indeed, what is it?
Etymology of the word
Let us begin with the origin of this word. According to the dictionary of the Russian language, a ray is a stream of light that emanates from some source, or a narrow strip of light emanating from a luminous object. For example, the rays of the setting or 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 hit their Old Slavonic.
Value and applications
The word “ray” is primarily associated with sunlight. How many times did everyone hear the expression: “sun rays” or “ray of light”. But in fact, this word is directly related to geometry. A ray is a part of a line that is limited on one side by a point and infinite on the other.
Any ray has an extreme point. This is the beginning of the beam. Since it has no end, it is usually indicated by a single letter. In addition, a ray is one of the simplest geometric shapes, such as a line segment or a broken line.
The concept of the beam is also used in physics, but only in acoustics and geometric optics. Here a ray is a line along which light energy moves.
The main feature of the geometric and light beam is their straightforwardness. But for light this is true only if it is distributed in a uniform transparent medium. Otherwise, it becomes curved.
How to see the light
Children will really like this experience; it will clearly show them what a ray of light is. This requires simple preparations. You need to darken the room and put any flashlight on the edge of the table. A ray of light is now barely visible, but it is only necessary to sharply squeeze a pre-prepared plastic bottle with talcum powder or baby powder, as particles of powder, once inside it, begin to glow. Now children can see that a light ray is a streak of light emanating from a flashlight and continuing into infinity. Why it happens? The fact is that the light cannot be seen until it reflects off some surface. Particles of talcum powder, falling into a ray of light, make it clearly visible.