In a longitudinal wave, compressions are regions where particles are closer together than normal. They are regions of higher pressure.
Compressions alternate with rarefactions (regions where particles are further apart). The distance from one compression to the next equals one wavelength.
In sound waves, a vibrating source pushes air molecules together to create compressions and pulls them apart to create rarefactions. This pattern of high and low pressure travels through the air as the sound wave.
Need help understanding this?
A 0625 specialist can explain this concept using the student's own questions and show how it appears in exam papers.