How are sound and light alike and different?

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Sound and light are similar in that both are forms of energy that travel in waves. They both have properties of wavelength, freqency and amplitude. Here are some differences:

  • Sound can only travel through a medium (substance) while light can travel through empty space.
  • Sound is a form of mechanical energy caused by vibrations of matter. Light is electromagnetic energy caused by interacting electric and magnetic fields. 
  • A light wave is a transverse wave, meaning that its displacement is perpendicular to its direction of travel. (Picture a sine wave or an ocean wave.) A sound wave is a longitudinal wave, meaning that its displacement is the direction it travels. It's also called a compression wave. Picture a Slinky toy (spring) being stretched and compressed longitudinally.
  • Light travels much faster than sound. It travels at a speed of about 300 million meters per second, while sound travels at about 340 meters per second depending on altitude and air temperature.
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