Question

Write difference between sound wave and light wave.

Answer 1

Hint:Sound waves travel through compressions and rarefactions and hence they need molecules which can travel through these distances while light does not need matter to travel. It travels with the help of imaginary particles called photons which do not need to get compressed.

Complete answer:
Light waves travel through the help of imaginary particles like photons, while sound waves need molecules to travel. Sound is obtained from the vibrations produced from the compressions and rarefactions of such sound waves. Light waves can propagate through vacuum as they do not disappear after some time and hence do not require medium for propagation.

However, sound waves are types of mechanical waves. Sound waves require a medium for its production and propagation. Sound waves are produced due to the vibrations of molecules of medium and as there is no matter in space the sound waves cannot propagate in vacuum. The speed of light in vacuum is $$3\times {10}^{8}m/s$$ while the speed of sound in vacuum is $$340m/s$$. Also, light waves are transverse waves while sound waves are longitudinal waves. Sound waves are longitudinal waves and hence they cannot be polarized but electromagnetic waves are transverse and they can be polarized.

Note: The speed of light in vacuum is the maximum velocity that can be obtained in the universe and nothing has ever been found which can exceed the speed of light. When lightning strikes, we will first see its flash and after a few seconds we could hear it because the speed of sound is lesser than the speed of light.