Waves and sound

What are waves?

Waves are vibrations that transfer energy from place to place without the matter being transferred.

Some waves must travel through a substance. The substance is known as the medium and it can be solid liquid or gas.Sound waves and  seismic waves are like this.They must travel through a medium.

Other waves do not need a medium to travel through a substance. They may be able to travel through a medium, but they do not have to. Visible light, infrared rays, and other types electromagnetic radiation are like this . They can travel through empty space.

Transverse waves
In transverse waves, the oscillations are at the right angle to the direction of travel and energy transfer.Light and other types of electromagnetic radiation are transverse waves. All electromagnetic waves travel at the same speed through a vacuum. 

Longitudinal waves
in transverse waves, the oscillations are along the same direction as the direction of travel and energy transfer.Sound waves are longitudinal waves they must travel through…