If the sound encounters objects that are of different density than the surrounding medium, such as fish, they reflect some sound back toward the source.

The optical breakdown is a very "violent" phenomenon and changes drastically the structure of the surrounding medium.

The greater the density of the surrounding medium, the stronger the force from dynamical friction.

This force depends on light intensity and particle size but has nothing to do with the surrounding medium.

In a thin section it has a high surface relief and will have sharp boundaries with the surrounding medium.

These stars start out spinning very rapidly and, in the process, sweep an intense magnetic field through the surrounding medium.

Here the temperature of the gas is practically the same as of the surrounding medium.

Then there was a quick ripping feeling, as though he had been plucked out of some sticky surrounding medium.

Normally when we look at paper the surrounding medium is air, with an index of refraction only slightly greater than 1.0.

"That's the business of ultrasound, to wiggle something that will then entrain movement in a surrounding medium."