Question

what is wave surface?

Answer 1

: a combination of wave fronts developed simultaneously from a single center (as of light in uniaxial and biaxial crystals)

the wave surface for a uniaxial doubly refracting substance consists of a sphere enclosing or enclosed by an ellipsoid of revolution

Answer 2

In physics, a surface wave is a mechanical wave that propagates along the interface between differing media. A common example is gravity waves along the surface of liquids, such as ocean waves. Gravity waves can also occur within liquids, at the interface between two fluids with different densities.