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Are colours an illusion??



Can you guess the colour of this dress? Some of you might say it’s blue and black and some of you will say it’s golden and white. So let’s understand why we see different colours and how can we exactly know which colour dress has.





WHAT IS COLOUR



Newton experimenting with Prism


Back in the 17th century, Sir Issac Newton was the first to study optics. He began his investigations by cutting a pinhole in his window shade to let in sunlight, which showed up on his wall as a round illuminated area. He put a glass prism in the way of light. He observed that one single white light gets dispersed into many colours! This experiment implied that what we see as a single white light coming from the sun is not actually white but a mixture of seven different colours. In a vacuum, all colours travel at the same speed, but when they get refracted by a prism due to their unique property (wavelength) they travel at a different speed. That causes colour formation.


Newton concluded that light is a wave. When this high-speed electromagnetic wave travels at around 3*10^8 m/s , it is dispersed by the atmosphere. When this light hits any object, it absorbs most of the light .But one of the wavelengths of light gets reflected by that object. This reflected wavelength hits our eyes, and we get to know colour of the object. Let me give you one example,there are two balls, red and blue. Fundamentally, the red ball is telling us that “I will reject the red colour but will absorb any other colours” and the blue ball is telling us that “I will reject only blue colour but absorb all other colours.” So when we put a red light on a red ball, it will reflect, and we will see the colour of ball as red. But this same red light we put on the blue ball, will make it appear black!! Why? Because as the blue ball was saying, I will absorb everything except blue! So factually speaking, objects that are yellow are not actually yellow but violet, indigo, blue, red, orange and green! To conclude this paragraph, We must understand that the colour of an object does depend on its light source. Light source matters!



Colour of the dress


So coming back to our original question. Whats the colour of the dress? There are high chances that people who saw colours as blue and black assumed that dress is kept in an artificial light source, e.g., a light bulb. And people who saw dress as white and golden would have assumed that dress is kept in natural light source. This phenomena is known as ‘Colour Constancy’. Our brain unconsciously tries to create an environment to determine the colour of objects. There is no way to end this debate without knowing the light source and surrounding. As the matter of fact,from different pictures of the same dress, it was confirmed that its colours are blue and black.

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