Which statement best describes light?

Which statement best describes light?

• A. A wave of alternating electric and magnetic fields
• B. It is a mechanical wave
• C. It is a sound wave
• D. It is a form of matter

Answer: (A)

Light is an electromagnetic wave: it travels through space as oscillating electric and magnetic fields that are perpendicular to each other and to the direction the light is moving. This description explains why light can move in a vacuum and carry energy without needing a material medium. It isn’t a mechanical wave, which would require particles to vibrate in a material; it isn’t a sound wave either, since sounds are mechanical waves in air or other substances. It’s also not matter—light has no rest mass and behaves as energy (and sometimes as particles called photons) as well as waves. So the statement that best describes light is a wave of alternating electric and magnetic fields.

Light is an electromagnetic wave: it travels through space as oscillating electric and magnetic fields that are perpendicular to each other and to the direction the light is moving. This description explains why light can move in a vacuum and carry energy without needing a material medium. It isn’t a mechanical wave, which would require particles to vibrate in a material; it isn’t a sound wave either, since sounds are mechanical waves in air or other substances. It’s also not matter—light has no rest mass and behaves as energy (and sometimes as particles called photons) as well as waves. So the statement that best describes light is a wave of alternating electric and magnetic fields.