Question

how are electromagnetic and mechanical waves different?
electromagnetic waves travel slower than mechanical waves.
electromagnetic waves can travel through a vacuum, but mechanical waves cannot.
mechanical waves can travel through a vacuum, but electromagnetic waves cannot.

Explanation:

Electromagnetic waves don't need a medium (can travel in vacuum), while mechanical waves require a medium (can't travel in vacuum). Also, electromagnetic waves (like light) travel at a very high speed (approx \(3\times10^{8}\ m/s\) in vacuum), much faster than most mechanical waves (e.g., sound waves in air at about \(343\ m/s\)).

Answer:

Electromagnetic waves can travel through a vacuum, but mechanical waves cannot.