Friday, 30 May 2014

Electromagnetic Waves

You might have heard people talk of electromagnetic waves. Radio waves, micro waves, visible light etc all form a part of electromagnetic spectrum. Electromagnetic spectrum is just a band or collection of electromagnetic radiations. Now you might think, what is an electromagnetic radiation? Let's dive in and find out.

James Clerk Maxwell first postulated the existence of electromagnetic waves that was confirmed by Heinrich Hertz. Maxwell's equations said that a changing magnetic flux would produce an electric field and changing electric flux would produce a magnetic field. So if you change the electric or magnetic field at high frequencies, it would produce the other and vice-versa. This would give us an electromagnetic wave

A unique characteristic of these electromagnetic radiations are, they can travel even in vacuum. How is this possible? We know that sound needs a medium to travel then how can EM radiations travel in vacuum? Simply because electromagnetic radiations are just electric and magnetic fields perpendicular to each other and these fields do not require any medium to travel.

The velocity of electromagnetic waves is constant, i.e. 3 x 10^8 m/s. This is equal to the speed of light. Hence James Clerk Maxwell concluded that light is also an electromagnetic radiation.