physics principle onmeasurement of the speed of sound in liquid using light?

Question

please give the physics principle on which this depends upon.

Answer 1

You've been reading that news story about physics students competing in Slovakia. I read it in a NZ newspaper today, and wondered about it too. The only answer I can think of is that the refractive index of the compression half cycle of the sound wave is slightly higher than that in the liquid in the rarefaction half cycle.