We typically deal with sound that has wavelengths comparable to the objects it i

Question

We typically deal with sound that has wavelengths comparable to the objects it interacts with (on the order of a few centimeters to a few meters), so we don't usually talk about "sound rays" Or Snell's law for sound. But if we are working with high frequency ultrasound, as is used in many medical probes, it would be appropriate to consider it. We are pretty certain of a couple of relevant facts about sound: Sound propagates as a wave. The speed of sound is greater in a dense medium. Discuss what this would mean for a Snell's law for sound. Do you expect a ray of sound coming into a denser medium to bend toward the normal (like light) or away from the normal? Explain your reasoning. Can we have the analog of total internal reflection for sound? If so, this could have severe implications for imaging using ultrasound. If it is possible to have total internal reflection for high frequency ultrasound, discuss the conditions under which this could occur Compare and/or contrast this situation to that of light.

Explanation / Answer

A_) sound will not follow snell's law.because it is also a wave but it will travel faster in denser medium.

You know that sound waves are Logitudanal and light exhibits Transverse wavy property in nature. Wait! This is not the answer.!

Sound does not interact with Matter. It just propagates through.

Let me put in points

1). A Dense media is composed of Large number of particles that are mutually interacting(ofcourse). So more the number of particles, more the mutual interaction among particles which leads to more absorption of sound and more vibrations are generated eventually making sound to pass through. Ofcourse, some sound is being dissipated(Wasted but little only).

2). Thus we say sound ismechanical vibrationsof molecules of media.

3). In vacuum no matter is physically exists so no molecules which means no vibrations. Thus sound does not propagate in vacuum.


But the case is reverse in light

1). Light excites electrons and impurities in the material.(This is not the answer)

2).(Important Experimental fact) Frequency of Light remains unaltered in the media(no matter dense of lighter). As you are aware mathematically
c = frequency x wavelength(c being speed of light) so

frequency = c/ wavelength

since frequency does not change, the only wave the above equation is satisfied by the very nature of universe is a sacrifise from velocity side and wavelength side. so c and wavelength change in such a way that frequency remains unaltered.
(This is more Mathematical but true so this is on of your answers)

B)You can basically achieve total internal reflection of sound in any medium as long as it is transmitting into a faster medium above the critical angle for that boundary. For example sound travels faster in hotter air. This means if sound was moving from cold air to hot air at a shallow angle to the boundary, you would have the total internal reflection of sound.

You could even have it travelling from air (340m/s) to water (1500m/s)

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