Question

Distance between adjacent compression and rarefaction

Answer 1

Distance between a compression and adjoining rarefraction is$\lambda $/2

Answer 2

Compression refers to the region of a longitudinal wave where the particles are closest to each other.
Rarefaction refers to the region of a longitudinal wave where the particles are farthest apart from each other.
In case of compression, the molecules contract and come closer to each other.
In case of rarefaction, the molecules expand and go far apart from the normal position.
In case of compression, the pressure and density increases.
In case of rarefaction, the pressure and density decreases.

Hope this helps!!!