Electromagnetic Waves
Electricity and magnetism were once thought to be separate forces.
However, in 1873, Scottish physicist James Clerk Maxwell developed a unified theory of electromagnetism.
The study of electromagnetism deals with how electrically charged particles interact with each other and with magnetic fields.
Light, microwaves, x-rays, and TV and radio transmissions are all kinds of electromagnetic waves.
They are all the same kind of wavy disturbance that repeats itself over a distance called the wavelength.
Magnetism can also be static like a refrigerator magnet. But when they change or move together, they make waves - electromagnetic waves.
Mechanical waves and electromagnetic waves are two important ways that energy is transported in the world around us.
Waves in water and sound waves in air are two examples of mechanical waves.
Mechanical waves are caused by a disturbance or vibration in matter, whether solid, gas, liquid, or plasma.
Matter that waves are traveling through is called a medium. Water waves are formed by vibrations in a liquid and sound waves are formed by vibrations in a gas (air).
These mechanical waves travel through a medium by causing the molecules to bump into each other, like falling dominoes transferring energy from one to the next.
Sound waves cannot travel in the vacuum of space because there is no medium to transmit these mechanical waves.
Electromagnetic waves are created by the vibration of an electric charge. This vibration creates a wave which has both an electric and a magnetic component.
An electromagnetic wave transports its energy through a vacuum at a speed of 3.00 x 108 m/s (a speed value commonly represented by the symbol c).
The propagation of an electromagnetic wave through a material medium occurs at a net speed which is less than 3.00 x 108 m/s.
This is depicted in the animation below.
Mathematical Representation
The mathematical representation of electromagnetic wave travelling in the x-direction is of the form as:
E(x,t) = Emaxcos(kx - ω t + Φ)
B(x,t) = Bmaxcos(kx - ω t + Φ)
Where in electromagnetic wave
E = electric field vector and
B = magnetic field vector
Maxwell gave basic idea of Electromagnetic radiations, whereas Hertz experimentally confirmed the existence of an electromagnetic wave.
The direction of propagation of the electromagnetic wave is given by the vector cross product of the electric field and magnetic field.
Applications of electromagnetic waves
Electromagnetic radiations can transmit energy in a vacuum or using no medium at all.
In communication technology the electromagnetic waves play an important role.
Infrared radiation is used for night vision in security cameras.