Optics - Fundamentals

Light - Behavior and Principles

THE light, or visible light as it is physically characterized, it is a form of radiant energy. It is the physical agent that, acting on the visual organs, produces the sensation of sight.

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Radiant energy is that which propagates in the form of electromagnetic waves, including radio waves, TV, microwaves, x-rays, gamma rays, radar, infrared rays, ultraviolet radiation and visible light.

One of the characteristics of electromagnetic waves is their propagation velocity, which in vacuum has a value of approximately 300 thousand kilometers per second, ie:

It may have this value reduced in media other than vacuum, being the slowest speed to date measured for such waves when crossing a compound called Bose-Einstein condensate, proven in a recent experience.

The light we perceive is characterized by its frequency that goes from the (red) to (Violet). This range is the sun's most emitting, so the visual organs of all living things are adapted to it, and cannot see beyond it, such as ultraviolet and infrared radiation.

Optics Divisions

Physical Optics: It studies optical phenomena that require a theory about the nature of electromagnetic waves.

Geometric Optics: studies the optical phenomena in which the trajectories followed by light are of interest. It is based on the notion of ray of light and the laws that regulate its behavior. High school study is restricted to this part of optics only.

Basic concepts

Light rays

They are the geometric representation of the light's trajectory, indicating its direction and the direction of its propagation. For example, in a point source infinite rays of light are emitted, though only a few of them reach an observer.

A ray of light is represented by a line segment oriented in the direction of propagation.

Light beam

It is a set of infinite rays of light; A light beam can be:

  • Converged tapered: the rays of light converge to a point;

  • Diverging tapered: the rays of light diverge from a point;

  • Parallel Cylindrical: the rays of light are parallel to each other.

Light sources

All that can be detected by our eyes, and other image-fixing instruments such as cameras, is the light from luminous bodies that is diffusedly reflected by the bodies around us.

Light source are all bodies from which light can be received, which may be primary or secondary sources.

  • Primary sources: Also called luminous bodies, are bodies that emit their own light, such as the sun, the stars, the flame of a candle, a light bulb,…
  • Secondary Sources: Also called illuminated bodies, are the light-sending bodies they receive from other sources, such as the moon, planets, clouds, visible objects that do not have their own light,…

As for its dimensions, a font can be classified as:

  • Point or point: a source without considerable dimensions that emits infinite rays of light.

  • Extensive: a font with considerable dimensions in relation to the environment.

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Light propagating means

The different material media behave differently when crossed by light rays, so they are classified into:

Half transparent

It is an optical medium that allows for the regular propagation of light, that is, the observer sees an object clearly through the medium. Examples: air, plain glass, cellophane, etc…

Translucent medium

It is an optical medium that allows only an irregular propagation of light, that is, the observer sees the object through the medium, but without sharpness.

Half opaque

It is an optical medium that does not allow light to propagate, ie it is not possible to see an object through the medium.