optical refraction

optical refraction

La optical refraction It is a phenomenon that occurs when light falls obliquely on the separation surface of two media, so the light changes direction and speed. It is widely used in optics and physics as well as in astronomy.

Therefore, we are going to dedicate this article to tell you everything you need to know about optical refraction, its characteristics and importance.

What is optical refraction

optical refraction examples

Optical refraction refers to the transfer of light waves from one material medium to another during the propagation process, and then their direction and speed immediately change. It is a process related to the reflection of light and can manifest simultaneously.

Light can travel in material media such as vacuum, water, air, diamonds, glass, quartz, glycerin, and various transparent or translucent materials. In each medium, light travels at different speeds.

For example, light is refracted when traveling from air to water, where the angle and speed of travel change. The following elements participate in any phenomenon of light refraction:

  • incident lightning: the ray that reaches the surface between the two media.
  • refracted ray: A ray of light that is bent when a wave travels across a surface.
  • Normal: Imaginary line perpendicular to the surface, established from the point where two rays meet.
  • Angle of incidence: The angle between the incident ray and the normal.
  • refraction angle: The angle between the refracted ray and the normal.

Optical refraction phenomenon


When light falls on a surface that separates two media, such as air and water, a part of the incident light is reflected, while another part is refracted and passes through the second medium.

While the phenomenon of refraction applies primarily to light waves, the concepts apply to any wave, including sound and electromagnetic waves.

The laws deduced by Huygens that govern the movement of all waves are fulfilled:

  • The incident, reflected and refracted rays lie in the same plane.
  • The angle of incidence and the angle of reflection are equal., understanding by such the angles formed by the incident ray and the reflected ray, respectively, perpendicular to the separation surface drawn at the point of incidence.

The speed of light depends on the medium through which it travels, for so the denser the material, the slower the speed of light and vice versa. So when light travels from a less dense medium (air) to a more dense medium (glass), the light rays are refracted close to normal, so the angle of refraction will be less than the angle of incidence.

Similarly, if a ray of light passes from a denser medium to a less dense medium, will refract away from the normal, so that the angle of incidence will be less than the angle of refraction.


We have already mentioned that optical refraction is a physical phenomenon that occurs when light passes from one medium to another with different densities. This phenomenon is of great importance in our daily life and in different fields of science and technology.

One of the most common examples of optical refraction is the formation of rainbows. When sunlight passes through water droplets in the atmosphere, the light is refracted and scattered at different wavelengths, thus creating the spectrum of colors we see in rainbows. This phenomenon is also used in lens optics and in the manufacture of optical instruments, such as camera lenses, microscopes, and telescopes.

In addition, optical refraction is fundamental in the correction of human vision. When light enters our eye, it is refracted through the cornea and lens to form an image on the retina. If the eye does not properly refract light, it can cause vision problems such as nearsightedness, farsightedness, and astigmatism. Contact lenses correct these refractive problems and allow light to be properly refracted into the eye.

In industry, optical refraction is used in the manufacture of transparent materials and the measurement of the concentration of solutions. In medicine, optical refraction is used to measure the density and refraction of biological tissues, allowing early detection of diseases.

Without optical refraction, imaging, vision correction, the manufacture of lenses and other optical instruments, disease detection, and many other scientific and technological advances that improve our quality of life would not be possible.

Examples of optical refraction

uses of lenses

Some common examples of optical refraction can be found in the following phenomena:

  • Teaspoon in teacup: When we put a teaspoon in a cup of tea, we can see how it crumbles. It is the effect of refraction of light that produces this optical illusion. The same phenomenon occurs when we put a pencil or a straw in the water. These curved illusions are created due to the refraction of light.
  • Rainbow: Rainbows are caused by the refraction of light as it passes through tiny droplets of water suspended in the atmosphere. As light enters this area, it breaks down and creates colorful effects.
  • sun halo: This is a rainbow-like phenomenon that occurs in certain parts of the globe or under very specific atmospheric conditions. This is created when ice particles accumulate in the troposphere, refracting light and breaking it up, making it possible to distinguish the colored rings around light sources.
  • Light is refracted in a diamond: Diamonds also refract light, dividing it into multiple colors.
  • Glasses and magnifying glasses: The magnifying glasses and lenses that we use are based on the principle of light refraction, because they have to capture the light and distort the image so that it can be interpreted with the naked eye.
  • sun in the sea: We can see sunlight changing angle and speed, and scattering as it passes across the surface and out to sea.
  • Light through stained glass: Light refraction also occurs through glass or crystal, which filters light and diffuses it into the environment.

I hope that with this information you can learn more about optical retraction and its characteristics.

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