Which wave interaction results in a change in the direction of the wave as it passes through one medium to another medium?

absorption

diffraction

reflection

refraction

Explanation :

The phenomena in which the ray of light bend towards or away from the normal is called the refraction of light. Light always travels in straight line. If the speed of light in both medium differs then refraction occurs.  

According to Snell's law :

Where and   is the refractive indices of two medium 1 and medium 2.

and   is the speed of light in medium 1 and medium 2.

Hence, the given figure shows the refraction of light.

d) the number of neutrons plus the number of protons