The refraction of light is when the light wave passes from one material medium to another when propagating, after which there is an immediate change in its direction and speed. It is a process related to the reflection of light and can occur at the same time.
Light can propagate in material media such as vacuum, water, air, diamond, glass, quartz, glycerin, and all kinds of transparent or translucent materials. In each medium, light travels at a different speed.
There is refraction of light when, for example, it passes from air to water, in which its angle and speed of movement vary.
In all light refraction phenomena, the following elements participate:
The speed of light in each medium is given by a magnitude called the refractive index. The refractive index of these material media is determined by calculating the ratio between the speed of light in a vacuum and the speed of the medium in question. The formula to calculate the refractive index is:
Today the refractive indices of many material media are known. Some examples are:
Two laws of light refraction are known that explain the behavior of this phenomenon.
According to the first law of refraction of light, the ray of incidence, the ray of reflection, and the line normal lie in the same plane. Consequently, when the phenomenon is observed from above we can capture continuity between both rays.
Snell's law or second law of refraction of light determines that this occurs when the refractive index of the two media is different and the light ray falls obliquely on the surface that separates them.
With this in mind, Snell's law establishes the formula for calculating the angle of refraction of light. It applies to any electromagnetic wave. It gets its name from the Dutch mathematician Willebrord Snell van Royen, who discovered it in the 16th century.
The formula for Snell's law is as follows:
n 1 sen θ 1 = n 2 sen θ 2
Some common examples of light refraction can be found in the following phenomena:
A teaspoon in a cup of tea
When we introduce a teaspoon into a cup of tea, we can see it as if it were divided. It is an effect of the refraction of light that produces that optical illusion.
The same phenomenon occurs when we put a pencil or a straw in water. The illusion is produced that these are bent due to the refraction of light.
A rainbow is produced by the refraction of light when it passes through small droplets of water suspended in the atmosphere. The light, when entering this area, breaks down and generates a colorful effect.
halos of sunlight
It is a phenomenon similar to the rainbow and that occurs at some points on the globe or in very specific atmospheric conditions. This occurs when ice particles accumulate in the troposphere, which refracts light and decomposes it, allowing a colored ring to be distinguished around the light source.
Refracted light in a diamond
Diamonds are also capable of refracting light, breaking it down into multiple colors.
Lenses and magnifying glasses
Both the magnifying glasses and the lenses that we use are based on the principles of light refraction since they must capture the light and deform the image so that it can be interpreted by the eye.
Rays of sunlight on the sea
We can see sunlight changing angle and speed, and it scatters as it enters the sea through the surface.
light through a stained glass window
The refraction of light also occurs through glasses or crystals, which filter the light and diffuse it in the environment.
The reflection and refraction of light are related, although different processes. The reflection of the light consists of its bouncing when it strikes a surface or interface that separates two different media. For example, the reflection of a landscape in a lake or of a face in a mirror is a light reflection phenomenon.
Instead, the refraction of light occurs when light passes through the surface that separates two media to continue its propagation. By penetrating the second material medium, the light beam will change its angle and speed.