Since times immemorial, the phenomenon of light has fascinated the human race. Scientists, physicists and men of learning have spent years dedicated to discovering the hidden nuances of this singularly interesting marvel of nature.
Living on Earth, we take for granted the yellow warmth of sunlight we’re bathed in every day. But did you know, there’s no light in outer space? We, on Earth, are able to perceive light courtesy our atmosphere which scatters the sunlight it receives into photons that are perceivable by the human eye. Earth is blessed to receive just the right amount of light energy from the Sun so that we can exist, survive, flourish. So how about delving into some of the more mesmerizing aspects of light? Here goes-
What Is Light?
This question has confounded scientists of all eras. Galileo, Einstein, Newton, Hubble and so many more distinguished men of learning throughout the history of science have concentrated their prodigious intellects on the matter.
And just when they think they’ve got it all figured out, light comes up with something new and totally radical that sets them thinking again. For example, it is accepted truth that light travels faster than anything else in the universe. And then, in 1999, Harvard University physicists passed a beam of light through the state of matter called Bose-Einstein Condensate (BEC) and brought down the speed of light to 61 kilometres per hour! Almost 18 million times slower than the normal speed of light! Light travelling at the speed of a car cruising comfortably down the highway- who would’ve thought that possible? Well, that’s the unpredictably perplexing nature of light for you!
So, what exactly is light? Light is a form of energy that travels in waves- electromagnetic waves, to be precise. It was in the 1860s that Scottish physicist James Clerk Maxwell described light as a very special kind of wave — one composed of electric and magnetic fields. Owing to this, light is also referred to as electromagnetic radiation. These electromagnetic waves of light do not need a medium to travel through. They can even travel in vacuum. When passing through vacuum, light travels at a speed of 300,000 kilometres per second. Scientists call this the speed of light, one of the most important numbers in physics.
Since light is actually waves, it is measured in wavelengths and frequencies. The electromagnetic waves of light occur over an extremely broad range of wavelengths, from gamma rays with wavelengths less than about 1 × 10−11 metre to radio waves measured in metres. The human eye can perceive only a very narrow band of this range- from about 700 nanometres (nm) (billionths of a metre) for red light to about 400 nm for violet light (white light actually consists of a spectrum of seven colours from red, orange, yellow, green, blue, indigo to violet).
Light is actually a form of energy. According to the Quantum Theory of Light, it consists of very small bundles of energy called photons. More the number of photons, brighter will be the intensity of the light, and vice versa.