THE Optics it is the part of physics responsible for the study of light and the phenomena associated with it. As light has a dual behavior and can be considered as a wave or a particle, studies in Optics are divided into two parts:
physical optics – when considering the wave nature of light;
geometric optics – when light is considered a particle and its studies are based on the concept of light rays, giving a geometric model to the light.
Important Definitions of Geometrical Optics
As the focus of this text is only on Geometrical Optics, before getting to know its principles, let's look at some important definitions:
You light rays are line segments that represent the direction and direction of moon propagationz. They can be issued by two types of source:
primary sources: that emit their own light, such as the sun, the flame of a candle or a lamp;
secondary sources: which reflect the light they receive from a primary source, such as the moon which reflects the light it receives from the sun, or a book, which can only be seen if it reflects the light it receives from a lamp.
Light sources can also be classified according to their size:
Extensive fonts: when they have considerable dimensions compared to the dimensions of the object to be illuminated. For example: a light bulb burning near a book;
Point sources: if the dimensions of the light source are considered negligible in relation to the object to be illuminated.
A set of light rays constitutes a beam of light. The light emitted by a point source propagates in all directions, so it is called divergent beam of light rays. When the rays are parallel, as in the case of light emitted by a flashlight, we say that the beam of light is convergent.
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The beam of light emitted by the flashlight has parallel light rays, that is, it is converging
Principles of Geometrical Optics
There are three principles adopted by Geometrical Optics to explain light phenomena.
The first is called Principle of Straight Propagation of Light and states that:
“In homogeneous and transparent media, light propagates in a straight line.”
This principle explains several phenomena, such as the geometric similarity between the shadow and the object that produces it, in addition to the formation of penumbra and eclipses.
The second principle of Geometrical Optics is that of independence from light rays, which has the following statement:
“When two or more light beams cross, one does not alter the propagation of the other.”
The two light beams intersect and continue to propagate in the same direction
Finally, the third principle, which is the reversibility of light rays:
“The path followed by light is independent of its propagation direction.”
THE Geometrical Optics is responsible for the study of various physical concepts, including the formation of shadow, dimness and eclipse; The reflection and the light refraction, as well as the formation of the image in mirrors, in the lenses and in optical instruments.
By Mariane Mendes
Graduated in Physics
Would you like to reference this text in a school or academic work? Look:
TEIXEIRA, Mariane Mendes. "What is Geometrical Optics?"; Brazil School. Available in: https://brasilescola.uol.com.br/o-que-e/fisica/o-que-e-optica-geometrica.htm. Accessed on June 28, 2021.
