Question

A wave which needs a medium (solid, liquid, gas) in order to propagate itself.

Answer 1

Longitudinal waves

Step-by-step explanation:

Mechanical waves are those waves which require medium to propagate. It has two types:

i) Transverse waves: These waves depend upon the rigidity of the medium so, they can propagate though solids and liquids but cannot pass through gases.

ii) Longitudinal waves: These waves depend upon the volume elasticity of the medium so, they can propagate through solids, gases, and liquids

Hence, the right answer is longitudinal waves.

Answer 2

The correct answer to the question is: Sound wave.

Step-by-step explanation:

Before going to answer this question, first we have to understand longitudinal wave.

A longitudinal wave is a mechanical wave in which the direction of propagation of wave is parallel to the direction of particle vibration.

This wave propagates through a medium in the form of compression and rarefaction.

Compression are the regions of high pressure zones where the particles of the medium are closely aggregated to each other.

Rarefaction is the region of low pressure where particles of the medium are not so close to each other as compared to compression.

The longitudinal wave can not propagate in space. It always needs a medium for it's propagation. The medium may be solid, liquid or gas .

For instance, sound wave is a longitudinal wave.

Hence, the correct answer of this question is sound wave which needs a medium for it's propagation.