Why do shorter wavelength pulses have greater penetrance in ultrasound?

Answer 1

In general, the shorter the wavelength, the greater the frequencey, and the greater the frequency, the higher the energy.

Here is a way to demonstrate that:

Take a rope, tie it to something and hold on to the other end with a little tension on it.

Move your arm up and down slowly, you will see long waves on the rope, but not to many. You are not using much energy to create these waves.

Now, go up and down faster, you will see shoter waves, and more of them. Yoy will also find youself getting tired faster because you are expending more energy to create the shorter waves.

That will drive the point home.

Answer 2

they have more energy.