# Mechanical waves transmission through different mediums

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1. Oct 9, 2015

### **Mariam**

1. The problem statement, all variables and given/known data
Do waves travel faster in dense or less dense mediums?

As a wave moves from a less dense to a denser medium at a boundary end what properties change? (Wavelength, speed, frequency, amplitude...)

If waves travel faster in solids then why do we hear better through air, and if we listen in water or solid it's deep and slow.

2. Relevant equations
-none- it's a conceptional question
But maybe these are helpful:
Frequency=1/ period
Speed=frequency*wavelength

3. The attempt at a solution

For the first question I previously thought that waves travel faster in more dense mediums, but I found this link. In the section about
"Transmission of a Pulse Across a Boundary from Less to More Dense"
It says the opposite.

So which is true ?

My second question is a result of the first and also refers to the same section in the link above. Why did the denser medium have a smaller amplitude and so did there reflected wave.

For my last question I don't have an idea on what might be the answer.

Thank you for your help in helping me understand this confusing topic, because I am currently really frustrated with y lack of understanding the topic for many weeks now.

2. Oct 9, 2015

### SataSata

I know that almost everybody I asked will tell me that mechanical waves like sound travel faster in denser medium. However that is actually not the case.
Initially I thought it had something to do with how sound is longitudinal while some other mechanical waves are transverse. I'm not sure how that relates yet.

The actual reason sound travel faster in medium that one might think to be denser is because of the 'elasticity' or 'tension' of the medium. It's about how much the medium wants to go back to its initial state.

The equation is v = sqrt(B/p) where B is the bulk modulus and p is the density. Bulk modulus is a measure of 'elasticity' of the medium. As you can see from the equation, speed is inversely proportional to density. Which means when density increase, speed actually decreases.

The reason I put ' ' on elasticity and tension is because I don't know the actual term and is my own way of explaining them.

3. Oct 9, 2015