How do you demonstrate the formation of compression and rarefactions in a slinky?

Explanation

1) Take a slinky.
2) It is a spring shaped toy which can be extrnded or compressed very easily.
3) Lay it down on a table or the floor as shown in figure.
4) Ask a friend to hold one end.
5) Pull the other end to stretch the slinky and then move it to and fro along its length.
6) We will see alternate compressions and rarefactions of the coil.
7) This is similar to the pattern of varying density produced in a medium when sound passes through it.
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