Question

which kind of wave would be observed in outer space between planets, where there is very little matter?
an electromagnetic wave, such as an x - ray
an electromagnetic wave, such as a sound wave
a mechanical wave, such as an x - ray
a mechanical wave, such as a sound wave

Explanation:

• Mechanical waves (like sound waves) need a medium (matter) to travel. Since there is very little matter in outer space between planets, mechanical waves cannot propagate there.
• Electromagnetic waves (such as X - rays) do not require a medium. They can travel through a vacuum (space with very little matter). Sound is not an electromagnetic wave. X - ray is an electromagnetic wave.

Answer:

an electromagnetic wave, such as an x - ray