When light passes through one medium and then passes to the other medium, it refracts. It occurs at the intersection of the two mediums. The speed of light varies depending on the medium. As a effect of the shift in light speed while moving from one medium to another, the phenomena of refraction happen.

In simple words, refraction is the bending of light as it passes through a transparent substance. Sound, water and other waves are also affected with these phenomena. Magnifying glasses, prisms, lenses, and rainbows are all possible because of this bending, which creates the refraction of the light. Without this phenomenon, our eyes would be unable to focus.

The following two findings lead us to believe that light bends at the interface between water and air namely when we put a pencil in a beaker containing, we see that it bends at the site where it just enters the water. Again, if we place a coin in the bottom of an empty glass and arrange our heads so that the coin is just out of sight, we can bring it into view by simply pouring water into the cup without moving our head or the cup.

Law of the Refraction of Light

The pattern of light as it passes through the interface of the two media is governed by the principles of refraction. Snell’s Law is the name given to it. As a result, we can say that light refraction is governed by two laws:

1. The ray of incident, the ray of refraction and the normal at the point of incidence of 2 transparent mediums are all in the similar planes.
2. The ratio of the sine of the angle of the incidence to the sine of the angle of the refraction is always constant for a given pair of media.

Cause of Refraction of Light

The refraction of light occurs whenever light passes through a medium with a variable refractive index or optical density. The change in speed is the reason for the change in direction. For example:

• When light travels from air to water, it slows down and changes its angle or direction when it is travelling.
• The degree of bending in light refraction is primarily determined by two factors:

The angle of incident rays– When the light enters a substance at a greater angle, the refraction of light is significantly greater and more visible to human sight. However, if light penetrates a substance at a 90-degree angle to the surface, it will slow down rather than change direction.

Change in Speed – When a substance causes light to speed up or slow down as it passes through it, the refraction of light increases.

Snell’s Law

Snells’ law is an important concept to define while learning about light refraction. The angle of the bending ray of light on the indices of refraction of two media is determined by this law. The Fresnel Equations or Fermat’s Principle can be used to obtain this statement. The formula for Snell’s Law is written as n1/n2 is equal to sin θ2/ sin θ1. The ratio of the sine of the angle of incidence to the sine of the angle of refraction is constant.

Kinds of Refraction

• Refraction of a light from a denser medium to a rarer medium: In this situation, the refractive index is less than 1 and the angle of incidence is smaller than the angle of refraction, causing the refracted ray to move 10 degrees away from the normal. Consider the following scenario: The refraction of light as it passes through glass and into the atmosphere.
• Refraction of a light from a rarer medium to a denser medium: In this scenario, the angle of incidence is greater than the angle of refraction, and the relative refractive index is greater than 1. As a result, the refracted beam tends to move closer to the normal. Consider the following scenario: Light from the air refracts in water.

Examples of the Refraction of Light

• The optical illusions of looming and mirage are caused by this phenomena.
• Because light from the bottom of the pool bent at the surface owing to refraction, a swimming pool appears to be shallower than it actually is.
• The sun rays bends through the rain droplets to form a rainbow, which is an illustration of refraction.
• Refraction of light splits white light into its component colours of orange, violet, blue, yellow, green and red when it travels through a prism.
• The refraction of light causes stars to twinkle.

Applications 

The refraction can be used in both optics and technology. However, the type of spherical lens used, be it concave or convex, has a significant impact.

• Lenses are the object that is transparent and that focus on light through refraction. Lenses are used in both cameras and binoculars.
• In cosmology, many telescopes are used to investigate faraway objects present in universe. In science, microscopes are routinely used to investigate extremely small objects which would otherwise be undetectable. These optical devices use refraction to enlarge images of small or distant objects.
• Prism is a wedge-shape device which is transparent and is widely used to extract a certain wavelength as optical filters. Light propagates at varying speeds in different materials, causing it to refract at various angles. This event is known as dispersion 
• Optical fibres, which are used for communication with the least amount of energy dissipation, are also essential for these phenomena.

Conclusion

Thus, we see that refraction is defined when there is shift in the direction of a wave as it travels from the one medium to the other medium. There are various application of it be it the telescopes, cameras, movie projectors and peepholes in home doors  all use this phenomena of the refraction of light.