Q: Given a scientific passage and an answer, generate a question for the given answer.
Passage: Water waves, sound waves, and the waves that travel along a rope are mechanical waves . Mechanical waves require a material medium such as water, air, or rope. Light waves, however, are electromagnetic waves and travel without a material medium. They are not mechanical waves. Answer: mechanical
A:
What waves require a material medium such as water, air, or rope?