水波同聲波既問題!!

Actually your point about water wave is wrong!!!!!
Water wave travel faster in deep water.As you know, the water in the deep sea is under high speed, and is more powerful than the one near the beach.As the wave is in the same medium, so its frequence is unchange. But its wavelength is decreased when it travel form deep water to shallow water. So as a result, the speed of the wave in shallow water is slower.
So the two wave is the same when they travel from denser medium to less dense medium!!!!!!!!!!!!

The velocity of mechanical waves depends mainly on two factors, the elastic modulus of the medium and the density of the medium.
In mathematical terms, it is,
v = square-root[E/d]
where E is the elastic modulus of the medium and d is its density.
Thus v will be slower if d is higher, i.e. the waves travel at a slower speed in high density medium if the elastic modulus remains the same. This is more or less true for water waves. Hence, waves in sea water (of higer density) travels slower than waves in fresh water (of lower density).
For sound waves, the elastic mouduls plays an important part, especially if you compare gas medium (e.g. air) with liquid medium (e.g. water) or solid medium (e.g. concrete, or iron). The elastic mouduls of solid is higher than that of liquid, whereas gas has got the lowest elastic modulus. As a reuslt, although the density of gas is lower than that of liquid and solid, the low elastic modulus of gas makes the quotient (E/d) to be the smallest among liquid and solid. This is why sound travels faster in lquids and solids than in air.


2007-07-02 20:23:41 補充：
For those who are not familiar with elastic modulus, it is an indication of the strength of intermolecular force between molecules....(contd)

2007-07-02 20:24:48 補充：
(contd)..... Intermolecular force is strongest in solids, weaker in lquids and the weakest in gases because of different distances of separation between molecules in the three matter states.