Re: Does the wavelength, wavespeed or frequency change during refraction?

By definition, refraction is defined by the change of at least two of those
measurements.

First, any type of wave (light, sound, surface water, vibrations on a
string/spring)will demonstrate a velocity dependent on the medium it
travels through. Light is fastest in a vacuum and moves slower in water and
still slower in glass. Sound travels faster in water than in air. Ripples
travel faster in deep water than in shallow. Sound travels faster in hot
gas than in cold gas. On a violin string it travels faster under greater
tension; so you "tune" a string instrument by changing the speed of the waves.

So when a wave (pick your choice) enters a different medium, it changes its
speed of propagation.

Frequencies are difficult to see and measure in many cases. Consider that
the vibrations could be measured before entering a new medium, inside the
new medium, and again upon exiting. If they were to decrease at the first
surface, we would have more waves going in than could come out. Hard to
explain. If they were to increase, there would soon be an infinite number
in the middle medium. Also hard to explain. For visible waves, we can see
that the frequencies do not change.

From wave equation, if the frequency is constant, the wavelength must be
inverse to the speed. This is also visible for water waves and for
vibrations on a spring. 

For one dimensional waves, there can be no change in direction. For surface
or 3-dimensional waves, they follow Snell's Law.

So yes, speed and wavelength change (inversely) and the frequency is
constant. The greater the density of the medium, the greater the changes
observed.