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 currently 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 means for Snell's law for sound. Do you expect a ray of sound coming onto a denser medium to bend towards 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. The speed of sound for some relevant media are given below. Determine which boundaries between two media could lead to total reflection of sound rays. Describe the configuration (entering from which medium) and find the angle above which total reflection occurs.*

Explanation / Answer

a)

i would expext to bend in the opposite direciton as light . the reason is that the sound travel faster in more denser medium ( light travel slower in more dense)

b)

since light bends away from the normal when speeding up we will get total internal refletion for air to muscle, air to bone and muscle to bone

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