# What is Critical Angle?

The angle of incidence, which generates an angle of refraction of 90 degrees and the refracted ray’s direction, becomes parallel to the interface between two media, is known as the critical angle. This phenomenon occurs when light travels through two media with different optical densities. The light wave, beyond this particular angle, is reflected rather than refracted, resulting in total internal reflection. Total internal reflection is a fascinating concept that is commonly used in everyday life, such as in optical fibers and the design of prisms.

# Explanation of Snell’s Law

Snell’s law governs the relationship between the angle of incidence and the angle of refraction, as well as the indices of refraction of the two media that the light passes through. The refractive index is a measure of the speed at which light travels through a medium. The law states that the sine of the angle of incidence multiplied by the refractive index of the first medium is equal to the sine of the angle of refraction multiplied by the refractive index of the second medium.

# Example of Critical Angle

A common example of the critical angle phenomenon is when we place a straw in a glass of water. The straw appears to be bent at the point where it enters the water. This effect is caused by the light refracting when it passes from the air to the water. The critical angle for water is approximately 48.6 degrees, which means that any incident angle greater than this will result in total internal reflection. Hence, no light can pass through the water, resulting in the appearance of the bent straw.

# Real-world Applications of Critical Angle

Total internal reflection has numerous real-world applications. Optical fibers are a prime example of these applications. They are used in telecommunication networks to transmit information over long distances. The light signals travel through the fibers by undergoing total internal reflection, which ensures minimal loss of information. Prisms are also an excellent example. Prisms are used to split light into its constituent colors. The critical angle of the glass prism is used to reflect light internally, which causes the refraction and separation of the colors. Additionally, diamond cutting is another application of critical angle. When a diamond is cut, the angles are set in such a way that they create total internal reflection, resulting in the diamond’s sparkling appearance.