Question

Which of the following require a medium for their propagation?
(A) Light (B) electromagnetic waves (C) microwaves (D) sound waves

Answer 1

Hint: In order to come in a position to answer this question we have to first be very thorough with the concepts of mechanical waves and electromagnetic waves and their distinctions. We can easily find the correct answer by distinguishing the given options into the two types of waves.

Complete step by step answer:
We know that mechanical waves are nothing but disturbances produced in a certain medium. A mechanical wave is a type of wave motion in which the particles of a medium oscillate and transfer energy throughout the medium. Mechanical waves require a material medium for their propagation and cease to propagate in the absence of a material medium such as a solid, liquid or gas. Since, sound waves are an example of mechanical waves; thus, they require a medium for their propagation.
Thus, option (D) is the correct answer to this question.

Additional Information: Electromagnetic waves on the other hand are very different from mechanical waves in the sense that they do not require any material medium for their propagation and can even travel through vacuum. This is because electromagnetic waves are not disturbances in medium but rather vibrations of electric fields and magnetic fields mutually perpendicular to each other.

Note: Any type of electromagnetic radiation can be distinguished from mechanical waves by the simple fact that all electromagnetic waves travel with the speed of light. Mechanical waves on the other hand do not have a fixed speed and thus, different mechanical waves travel with different velocities. Some mechanical waves like sound waves have high velocities while some mechanical waves like water waves have very low velocities.