Question

Fix up one end of a slinky to a hook and hold it horizontally. Vibrate the other end to and fro along the length of the spring. If you look at the spring carefully , you will see some parts of the spring are pushed closer , while some other parts are pulled apart.Then which of the following statements are correct about above experiment?

• A. The portions which are pushed closer are called compressions
• B. The portions which are pulled apart are called rarefactions
• C. Both A and B are correct
• D. Neither of A and B is correct

Answer 1

The correct option is C Both A and B are correct

Consider a vibrating tuning fork.

A vibrating tuning fork is capable of creating a longitudinal wave. As the prongs of the fork vibrate back and forth, they push on neighboring air particles. The forward motion of a prong pushes air molecules horizontally to the right and the backward retraction of the prong creates a low-pressure area allowing the air particles to move back to the left.So the air molecules also move in longitudinal manner.

Because of the longitudinal motion of the air particles, there are regions in the air where the air particles are compressed together and other regions where the air particles are spread apart. These regions are known as compressions and rarefactions respectively. The compressions are regions of high air pressure (particles are closer) while the rarefactions are regions of low air pressure(particles are farther).

The slinky experiment is just like the sound waves.The spring behave as the medium so spring body parts show longitudinal vibrations like sound so some part of slinky is in compression (spring is compressed) while some part is in rarefaction (spring is pulled apart) .