Above: Image © NejroN, iStockphoto.com


How do invisibility cloaks work? Is it just in Harry Potter or do they exist in reality?


The magic powers of Harry Potter may not be that far off in the real world! A team of physicists from the United Kingdom and the U.S.A. have just revealed a device that can make an object invisible. Only five months ago, the physicists theorized that at a specific speed the waves of light should be able to curve around an object and emerge on the other side as though they had passed through empty space. To move the light around an object, they proposed surrounding it with something called a "metamaterial." Metamaterial is an assembly of c-shaped rings and rods that allows the speed of light to be controllable. It works because when light travels through the metamaterial, the electrons in the rings and rods alter the speed of the light waves. Their theory thus predicted how the speed of light must vary in order to get it to travel along this path. The next task was to test this theory by designing a metamaterial cloak that could perform like they predicted, i.e. change the speed of light in a specific way. This week they announced success! They successfully designed an invisibility cloak, (which is not really cloak-like), out of metamaterial. Their cloak is a two-dimensional ring of side-by-side C-shaped copper rings. Objects that are surrounded by the metamaterial ring appear invisible when they are viewed in microwaves of a specific wave length that are polarized perpendicular to the ring. Although the cloak does not yet work for visible light, the scientists are optimistic that now that they have figured out how to make a cloak for microwaves that invisibility cloaks for visible light should be possible too. Watch out Voldemort!

Answered By: Dr. Christine


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