How are sound waves different from light waves?

1 Answer

Sound waves are longitudinal and require a medium for propagation.

Air molecules, for example, collide and move across a room in response to sound waves. Ears are sensitive to the motion of air molecules and our brains translate that motion into electrical signals, which we interpret in a variety of ways.

The presence of air molecules is essential to the propagation of sound waves. "In space", as the great poster from Alien 1 proclaimed, "no one can hear you scream". Along the same lines, exploding space ships in Star Wars are a figment of Hollywood hype. In space, no one can hear ships explode.

Light waves, like all forms of electromagnetic energy, are transverse and do NOT require a medium for propagation. They move freely through space from one end of the universe to the other.

Moreover, light waves, which are transverse, are composed of electric and magnetic fields which propagate perpendicular to each other. All transverse waves have this characteristic.

Sound waves, on the other hand, are longitudinal, which means that particles move parallel, rather than perpendicular, to the direction of motion of the sound wave.