Write the definition of note, tone, rarefaction and compression.

Hint: In order to solve this question we need to understand how sound waves travel? Does it require a medium to travel? So Sound wave is a longitudinal wave which requires a material medium to transfer from one place to another. Actually what happens is that sound waves are the result of vibration of atoms at their own places so when they vibrate they collide with other atoms nearby so sound energy gets transferred, this vibration has a pattern and we call it a sound.

Complete answer:
Rarefaction: So when a sound wave travels in medium as stated it atoms vibration so when the vibration is such that two atoms are far away from each then this is known as refraction

Compression: Due to atoms, vibration about their mean position creates a sound wave. So when vibration as such that two atoms are very close to each other while vibrating this is known as compression.So sound wave could also be considered as consecutive refraction and compression.Also these vibrations are not perpendicular to displacement of wave so it is known as longitudinal wave

A Note: When a sound wave is produced by different frequencies togetherly mixed it is known as a note.

Tone: So as stated earlier, vibration of atoms about their mean position has a pattern, it can be regular or complex. Regular pattern is one in which the atoms vibrate with one frequency known as tone.

Note: It should be remembered that sound wave speed is not constant. It depends on material medium refractive index also since it is a longitudinal wave so it travels much slower in comparison to light speed and that is the reason why you experience flash of light first and sound of lightning later.