Consider a wave along the length of a stretched slinky toy, where the distance between coils increases and decreases. What type of wave is this

"Longitudinal wave" is the appropriate answer.

Explanation:

The waves are longitudinal.

Explanation:

There are two types of waves:

Longitudinal waves : The waves in which the particles of medium vibrates in the same direction a the wave travels. Ex: sound waves  

Transverse waves : The waves in which the particles of medium in the perpendicular direction of the wave propagation. Ex: light waves.

The wave is travelling along the length of the slinky toy. So, the direction of motion of particles is same as the direction of motion of wave.

So, the waves are longitudinal in nature.

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