Phenomena of Deviation of Light by a Prism

As both phenomena are essential in the field of ray optics. Refraction is the bending of light waves while moving from one substance to another due to a change in the density of the substance. On the other hand, dispersion of light happens due to the movement of light from one medium to another and then it splits into different hues because of the refraction phenomenon and Snell’s law. This article will help in understanding these phenomena more. 

Definitions and concepts 

Refraction 

Refraction is an essential phenomenon that comes under ray optics. Refraction is a phenomenon in which light bends when it moves from one medium to another. It follows a single direction pathway until or unless changing of the medium.

In other words, refraction is a process of changing the pathway of light due to a change in velocity while moving from one medium to another medium. In a more straightforward form, refraction is a bending of light waves while moving from one substance to another due to a change in the density of the substance. 

For instance, light travels faster in the air (rare medium) than in water (dense medium) due to a change in velocity. On the other hand, the speed of sound waves is higher in warm air than in cold ones. 

This phenomenon can also be seen in the water, sound and other waves. Some examples are based on this process, such as prisms, lenses and rainbows. Even our eyes can see and focus due to the refraction of light.  

Laws of refraction of white light 

There are mainly two laws based on this phenomenon mentioned below:

• The incident ray, reflected ray and normal all lie at the point of incidence of two media on the same plane. 
• The ratio of the sine of the reflected angle to the sine of the incident angle is constant. This is also referred to as Snell‘s law of refraction.

Any white light is composed of seven colours of the rainbow and due to the process of refraction, these colours are split down into red, orange, yellow, green, blue, indigo and violet. Refraction can generate a spectrum, according to Issac Newton. He showed this through his triangular block experimentation called a prism. 

Prism 

In optics, it is a slab of glass or other transparent substance with specific angles and plane faces. It is useful for understanding the phenomenon of refraction. Any basic triangular prism can split the white light into its component colours and call it a spectrum. 

Dispersion of light 

Separating all the colours that compose the white light after passing through the glass prism is known as dispersion of light and divided light is the spectrum. 

In other words, the dispersion of light happens due to the movement of light from one medium to another. It splits into different hues because of the refraction phenomenon and Snell’s law. The white colour seems simple, although it consists of all the hues in its visible spectrum. Even though these hues are very new to each, the refractive index of each colour is different. Due to variation in the refractive index, each colour follows a different pathway. Hence, their deviation depends upon the wavelengths of hues. 

VIBGYOR and spectrum 

The colours consisting of white light are violet, indigo, blue, green, yellow, orange, and red and this can be memorised through the short form VIBGYOR. This band of all seven hues is the spectrum of white light. All the spectrum colours bend at different angles in terms of incident angle. Furthermore, red light bends the most and violet light bends the least. 

Examples of some natural phenomenon based on these processes

Formation of the rainbow: The natural example of the phenomenon of dispersion of light is the formation of a rainbow. Any rainbow is formed due to the refraction of each light spectrum with a sorely different angle after entering the tiny drops and reflecting off from the inside and then the light leaves the small drop.  

Atmospheric Refraction: When the refraction of sunlight occurs due to the earth’s atmosphere as it consists of many layers of different densities, this process is referred to as atmospheric refraction. 

Changing position of stars: Due to atmospheric refraction of earth, stars lighten up. On the other hand, the temperature and density of various layers of the atmosphere are changing and hence cause the changing position of the star. 

Conclusion

Hence, refraction of light and dispersion of white light are two crucial processes in ray optics. There are two laws associated with the refraction of light. The formation of the rainbow, the twinkling of stars, changing positions of stars, etc., are some natural phenomena based on these two. Dispersion is a widely used process in many natural incidents.