Everyone knows, or at least heard, that light has the property of refracting and reflecting. But only the formulas of geometric and wave optics can explain how, or rather, on what basis this is happening. And all this doctrine is based on the concept of the "ray", which was introduced by Euclid three centuries BC. So what is a ray, in scientific terms?
A ray is a straight line along which light waves move. How, why - the formulas of geometric optics, which is part of wave optics, answer these questions. The latter, as might be supposed, considers the rays as waves.
Geometric Optics Formulas
The law of rectilinear propagation: a ray in the same medium has the property of propagating rectilinearly. That is, the light moves along the shortest path that exists between two points. You could even say that a light beam seeks to save time. This law explains the phenomena of shadow and partial shade.
For example, if the light source itself is small in size or at such a large distance that its size can be ignored, then the light beam forms clear shadows. But if the light source is large or at a very close distance, the light beam forms fuzzy shadows and penumbra.
Law of Independent Distribution
Light rays tend to propagate independently of each other. That is, they will not affect each other in any way if they intersect or pass through each other in some kind of homogeneous environment. The rays do not seem to suspect the existence of other rays.
Law of reflection
Imagine a person pointing a laser pointer at a mirror. Of course, the beam will be reflected from the mirror and will propagate in another medium. The angle between the perpendicular to the mirror and the first beam is called the angle of incidence, the angle between the perpendicular to the mirror and the second beam is called the angle of reflection. These angles are equal.
The formulas of geometric optics reveal many situations that no one even thinks about. For example, the law of reflection explains why we can see ourselves in a “direct” mirror exactly the same as we are, and why its curved surface creates a different image.
Formula:
a - angle of incidence, b - angle of reflection.
a = b
Law of refraction
The ray of incidence, the ray of refraction and the perpendicular to the mirror are located in the same plane. If the sine of the incident angle is divided by the sine of the refracted angle, then we get the value of n, which is constant for both environments.
n shows at what angle the beam passes from the first medium to the second, and how the compositions of these media relate.
Formula:
i is the incident angle. r is the refracting angle. n 21 is the refractive index.
sin i / sin r = n 2 / n 1 = n 21
The law of reversibility of light
What does the law of reversibility of light say? If the beam propagates along a definitely built path in one direction, then in the opposite direction it will repeat the same route.
Summary
The formulas of geometric optics in a somewhat simplified form explain how a light beam works. This is nothing complicated. Yes, the formulas and laws of geometric optics neglect some of the properties of the universe, but their importance for science cannot be underestimated.