In which medium do waves travel fastest - air or iron?

Question

At one point, my text book states that the speed of sound is approximately 5000m/s in iron (desnity = 7.9 g/cm^3) and about 330 m/s in air (density = 0.001 g/cm^3). However, it then states that: "WAVES WILL TRAVEL FASTER IN AIR THAN IN IRON, BECAUSE THE AIR IS LESS DENSE." Is it just me or is this statement false?

Can someone please give a detailed sceintific explanation to how the velocity and wavelength of waves change as they enter different media?

Answer 1

Waves speed is relative to its starting point.
By definition and observation a wave is the physical response of a medium when disturbed.A wave would not exist with out a medium, because the oscilliatory motion of the medium is the wave.
The velocity of the wave increase in proportion to the density of the medium..Therefore air or gas being the less dense than solids would carry a wave at a lower velocity.Sound in iron or steel would carry sound At a higher velocity. The same is true with sea water sound travels much faster under water than in air.

Answer 2

I travel my fastest through a vacuum, where I have the least interference That speed is 186,000 miles per second. I am compressed while passing through a medium denser than a vacuum. This appears to make me go slower, but I regain my size and speed by expansion when leaving the denser medium. I simply bounce around like a ball until some electrical conductor cuts my magnetic lines of force causing me to move electrons sideways in the conductor. Which way I drive the electrons depends on which way my magnetic lines of force are oriented.
so i think waves travel faster in iron medium compare with air.

Answer 3

It's not just the density that determines the speed of sound. The molecular elasticity also is important, as well as the temperature and pressure.

That said, I think the statement is false; it seems some kind of mistake. Longitudinal sound waves travel faster in iron (about 5950 m/s) than in air (about 343 m/s).

Answer 4

You are obviously talking about sound waves and their propogation.

Just think of it like this, in a solid such as iron, the atoms that make up the bulk material are very closely packed as opposed to that of air (a typical mixture of gases) where the atoms are quite far apart when compared to a solid.

It would make sense that the closer the atoms are together the sound will propogate faster, as sound is just the transfer of vibrational energy.

Usually sound will travel fastest through solids, slightly slower through liquids and slowest of all through gases - remember sound must have a medium to propogate through - it cannot travel in a vacuum.

Answer 5

Take a look at

http://en.wikipedia.org/wiki/Speed_of_sound

The statement in the book would appear to be simply false, sound does travel much faster in iron. As the Wikipedia article states, increased density slows sound down, but increased stiffness speeds it up, and iron is very stiff.

Answer 6

general rule is that sound waves travel faster in denser mediums. but when it comes to solid , it should be metallic medium then they will travel faster .. not wood or glass etc.

Answer 7

the denser the medium the faster the speed or propagation of a wave.

Answer 8

v=(b/d)^(1/2) for air
v=331 m/s
b=bulk modulus of air=1.41*10^5
d=density of air=1.29

v=(y/d)^(1/2) speed of sound for iron
v=5140 m/s
y=youngs modulus of iron=19.0*10^10
d=density of air=7.2*10^3

thus sound wave travel faster in iron.

Answer 9

Iron.