Light refraction is one of the most well-known effects, but other waves, such as sound and water waves, can also refract. We may use optical devices like magnifying glasses, mirrors, and prisms, regardless of refraction. We can also centre light on our retina because of the refraction of light.

In optics and technology, refraction has various uses. The following are a number of the most well-known applications: 

• For different reasons, such as magnification, a lens uses refraction to create a picture of an item. 
• Spectacles worn by people with defective vision use the principle of refraction. 
• Peepholes in house frames, monitors, movie projectors, and telescopes all utilise refraction.

In optics, total internal reflection refers to the full reflection of a beam of light from the outer objects back onto a medium such as water or glass. If the angle of incidence approaches a certain limiting angle, defined as the critical angle, the anomaly arises. Complete internal reflection happens as a ray of light from a medium with a higher index of refraction enters the other medium at an angle of incidence greater than the essential angle at the border between two transparent media. The critical angle for a water-air surface is 48.5°. Since refraction indices are wavelength-dependent, the critical angle (and thus, the angle of complete internal reflection) differs marginally with wavelength and, thus, with colour. Both refraction and reflection arise in differing amounts at all angles less than the critical angle.

The following are a few explanations of how absolute internal reflection may be used: 

• System of communication 
• Windshield wipers and rain indicators for cars 
• Tools for optical fingerprinting

Lenses are simply curved-side magnifying lenses. By refraction, a lens is a fragment of translucent glass that concentrates or disperses light rays when they travel through it. Lenses are used in telescopes and other magnifying instruments because of their magnifying properties. They are used to collect light rays and are used in sensors. 

In cameras, light is captured using a collection of lenses rather than a single lens. The relationship between the size of the picture created by a lens and the size of the target is known as magnification. Lenses may often be used in groups to eliminate blurriness or distortion in the picture produced by the lens.

A prism is a translucent solid body with three rectangular lateral surfaces and two triangular faces that are inclined at an angle, as described in optics. 

As white light travels through a prism, it creates a rainbow of seven shades, showing that white light is a combination of seven colours. Prism only works as a separating medium for the seven shades. Refraction occurs as light strikes the glass prism. Since the wavelengths of various components of light vary and the frequency stays constant, the difference in velocity in the glass medium allows each object to deviate by a particular angle. The colour red, which has the longest wavelength, deviates the least and forms the upper half of the spectrum, while violet, which has the shortest wavelength, deviates the most and forms the lower portion.

Infrared light, X-rays, microwaves, and ultraviolet radiation are forms of electromagnetic radio waves that are visible. These waves may be visualised as the colours of the rainbow, with each hue containing a different wavelength. The wavelength of red is the highest, while that of violet is the smallest. When all of the waves are visible at the same moment, white light is produced. As white light travels through the lens, it is split down into the visible light spectrum’s colours. 

For various frequencies and wavelengths, EM radiation may be emitted as waves or ions. The electromagnetic spectrum refers to this broad range of wavelengths. It’s split into seven parts, with wavelengths declining and energy and frequency rising.

In this chapter, we learned about the basic concepts of light. We learned about the propagation and refraction of light.

1. In physics, what is light?
   The word ‘light’ is often used in science to refer to electromagnetic radiation of any wavelength, apparent or not. Gamma rays, X-rays, microwaves, and radio waves are also light in this way. A photon is the absorbed energy of EM waves and reflects the quanta of illumination. 
2. How can light propagate?
   Rays are light waves that propagate in straight lines from their source. 
3. What are the three fundamental characteristics of light?
   Frequency (f), wavelength (w), and photon energy (p) is the most general terminology used to define light quanta. 
4. What is the concept of light energy?
   Electromagnetic radiation contains light energy. Light consists of photons, which are generated as an object’s atoms heat up. The only source of energy apparent to the naked eye is light, which travels in waves. 
5. When it comes to light, where does it travel the fastest?
   Explain because, unlike sound, light waves move fastest in a vacuum and through the air and slower through other components like glass or water.