What Ancient Indian’s Knew About Optics, Lens and Rainbow Formation

rainbow and lensShloka: Aprapyagrahanam

Kayabhrapatalasphatikantaritopalabdheh ||

Meaning: That which cannot be perceived (with naked eye) can be perceived with (lens made of) glass, mica or crystal.

Shloka: Suryasya vividhavarnah pavanena vighaitah

Karah sabhre |

Viyati dhanuh samsthanah ye drsyante

Tadindradhanuh ||

Meaning: The multi coloured rays of the sun being dispersed by wind in a cloudy sky are seen in the form of a bow which is rainbow.

Source: Nyaya-darsanam, Adhyayah 3, Sutram 46, Kanadah (800 BCE), Brhat-samhita, Slokah 35, Varahamihirah (6th century AD)

Ancient Theory According to ancient Indian theories the optics came into light in the early 5th – 6th century BC. Sushrutha proposed to world that light which falls on the retina illuminates the world. It is the lens in the eyes that provides clear vision of far of objects. The naked eye vision is restricted to certain limit. And if there is to view something beyond it, then it is only possible via lens. Lens is made up of glass, mica or crystals. It is a small circular aperture which enables clear vision of far away objects.

Ancient scientist Varahamihira explained the rainbow concept in his book Brihat Samhita. He states that reflection is a phenomenon caused due to back scattering of particles. Rainbow has always been a touchstone for scientists to test various optic theories. They say that sun light is also a part of rainbow. The rainbow is seen after a day shower. When there is shower during a sunny day the sunlight passes through the rainy clouds and shows up in seven different colours in the form of bow which is known as rainbow.camera


Modern theory

Lens are usually made up of glass or a plastic fabric. There are two types of lens namely concave lens and convex lens. This classification is based on the aperture. Convex lens are used for viewing far off objects and concave lens are used to view near objects. There are so many things which are not visible to our naked eyes.

To view something very far off like space objects we use telescope which has concave lens. But some telescopes have the combination of both concave and convex lenses. And to view Nano or micro sized objects we use microscopes which have lens in them too. It is the aperture of the lens which makes this difference in perception.

Rainbow is one of the beautiful natural phenomenon. The sky just looks amazing when there is a rainbow occurring in the sky. Rainbow is a result of dispersion, reflection and refraction of light. Rainbow occurs only when there is rain as the rain drops serves as medium for the dispersion of light. When the clouds breakdown in the form of rain, sun light passing through rain drops gets dispersed. And this light gets refracted and reflected back.

In a primary rainbow the violet is in the inner part and red is in the outer part of the arc. The light entering into the water droplet gets refracted, then the refracted light gets reflected back and again gets refracted while coming out of the water droplet. This how a beautifully rainbow is formed.droplet

, , , , , , , , , image-cta

Leave a Reply

Your email address will not be published. Required fields are marked *