How are sound and light waves different?

Expert Answers
ms-ahmed eNotes educator| Certified Educator

Sound and light both travel in waves, which are caused by vibrations.  The vibrations begin when an object at rest is set in motion (e.g. a guitar string or electrons).  This vibrating motion can begin (initial displacement) in two ways, longitudinal or transverse.  Light waves are transverse.  This is when the movement of electrons is perpendicular to the motion of the wave.  An example is a football stadium wave.  Everyone is waiting for their turn, and when it comes, they sit and stand in an up and down motion, and the wave continues forward.  Light waves, therefore, move faster than sound waves, which are longitudinal.  Light waves can also travel through space.   

In the case of sound waves, which are longitudinal, the vibrations begin when a movement is made that is parallel to the wave path (a push instead of a rise).  This is sort of like a slinky being pushed, the wave that comes from it moves away from it in a parallel direction, without moving up and down.  Sound waves, being longitudinal, are slower than light waves, and do not travel through a vacuum (e.g. space).

  Finally, and again, because of their initial displacement and type of motion, sound waves travel faster through denser mediums (solids), while light waves travel faster through less dense mediums (gases).

thewanderlust878 | Student

Sound and light waves are very different, even though they are both considered to be "waves". Perhaps the biggest difference between the two would be how they travel around. Sound requires some form of medium to travel, because it is mostly a change in pressure. For example, with air, the change of air pressure would be the form of transportation for sound waves. Or water, where the water pressure would be how the sound moves. 

Light, however, is an electromagnetic wave. This means that it needs a combination of electricity and magnetic fields in order to travel places. Which means that it does not require air, water, etc, to travel. 

They also differ in speed. Sound travels at about a foot per millisecond, while light travels at about 186,000 miles per second. 

Hope this helps!

udonbutterfly | Student

Sound waves travel a lot slower than light waves. Unlike light sound waves requires a medium to create song. A guitar would be a great example if someone does not pluck the strings then sound is not heard right? Then when the strings are plucked sound travels the air. Light on the other hand travels really fast in a short amount of time. Although both are considered to be wave lengths they havea lot of properties.

rupkaur2001 | Student

You must have heard that sound cannot travel in vacum while light can

Well, thats right

Because light waves are electromagnetic rays while sound waves are mechanical

Electromagnetic rays have the ability to traverse through vacuum but  sound waves have to have a medium in order to be propagated.

E.g. we all know that the light reaching us from the sun is a result of the reactions takig place there. Well a lot of heat is also generated as sound and thank god, it doesnt reach us due to the lack of matter between the sun and the earth

Access hundreds of thousands of answers with a free trial.

Start Free Trial
Ask a Question