Question

Which of the following statements are correct?
i) Sound is produced by vibrations.
ii) Sound requires a medium for propagation.
iii) Light and sound both require a medium for propagation.
iv) Sound travels faster than light.
A) i & ii only
B) i, ii & iii only
C) ii, iii & iv only
D) iii & iv only

Answer 1

Hint: Think about what types of waves are sound and light. Recall the properties of sound and light and the types to which they belong. Also think which the fastest thing in the world is.

Complete step by step solution:
Sound is a mechanical wave and light is an electromagnetic wave. Thus sound needs a medium to travel. But light does not need a medium to travel.
Sound is produced by the to and fro motion or the vibrations produced in an object, these vibrations propagate through the medium to finally reach the receiver.
Light is the fastest thing in the world. Nothing can travel faster than light.
Thus statements (i) and (ii) are correct and statements (iii) and (iv) are incorrect.

Hence option (A) is correct.

Additional Information:
A wave is defined as the transfer of energy from one point to another. There are two large, all encompassing categories of waves: mechanical and non-mechanical. Mechanical waves are waves that require a medium for the transfer of their energy to occur. Water waves are an example of mechanical waves. Sound waves are another type of mechanical wave. They are compression waves that have a frequency between $20 - 20000Hz$ and travel through dry air at a speed of approximately $340m/s$ at room temperature. As a mechanical wave travels through a medium, it loses energy to the medium. The wave can only propagate through a limited distance.

Non-mechanical waves are waves that do not require a medium for the transfer of their energy to occur. Electromagnetic waves are the only type of non-mechanical waves. They can travel through the vacuum of space. Light from distant stars travels hundreds of thousands of millions of years to reach us. Although the electromagnetic radiation spans a large spectrum of wavelengths and frequencies, all electromagnetic radiation travels through a vacuum at $3 \times {10^8}m/s$ .

Note: Also do keep in mind the other types how waves are classified such as longitudinal and transverse waves. Do not confuse between mechanical waves and longitudinal waves.