Question

The electromagnetic wave travel in free space with the velocity of
a) Sound
b) Light
c) Greater than that of light
d) Greater than that of sound

Answer 1

Hint: These waves are formed due to the interaction of electric and magnetic fields. They are capable of travelling in every type of medium be it air, water or even vacuum. They can further be divided into various categories but share some common properties.

Complete answer:
 Electromagnetic waves are those waves which come into existence due to the vibrations between the electric field and the magnetic field. As a result, the name is given Electromagnetic Wave. Hence, we can say that the composition of an electromagnetic wave is nothing but an oscillating electric field and magnetic field. These two fields are perpendicular to each other.
There are different types of electromagnetic waves, all differing from one another in their basic characteristics. Some of the examples of electromagnetic waves are radio waves, microwave, gamma rays etc. Although there are various characteristics in which these waves have differences, there are various properties which these waves share in common. One of these properties is the speed at which they all travel. All the electromagnetic waves travel with the speed of light irrespective of their basic characteristics differences.
All the electromagnetic waves travel at a speed of $3\times {10}^{8}m/s$, which is the speed of light. These waves don’t need any material medium to travel as required by other mechanical waves like sound waves.
Hence, all the electromagnetic waves travel with the speed of light in free space.

Thus, the answer is option (b).

Note:
Electromagnetic waves are a composition of oscillating electric and magnetic fields. These fields are present at an angle of $90{}^{\circ }$ to each other. They are the only waves which travel at speeds close to the speed of light and don’t need any material medium to travel.