Why does a mechanical wave require a medium for transmission?
- the medium provides the required energy needed to propagate the wave.
- the wave is only transmitted when particles bump into each other.
- the medium keeps the wave from propagating too far.
- the medium provides an opposing force to slow down the wave.

- The wave is only transmitted when particles bump into each other.

Explanation:

A mechanical wave is a type of wave that propagates through a medium, carrying energy through the medium due to the oscillations of the particles inside the medium.

Due to its nature, a mechanical wave is transmitted through the collisions of the particles of the medium with each other: the closer the particles are, the faster the wave is transmitted (this is why mechanical waves travel faster in solids than in liquids or gases). Mechanical waves cannot be transmitted in vacuum, because there are no particles that can bump each other transmitting the oscillation.

Based on this definition, the correct answer is

- The wave is only transmitted when particles bump into each other.

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