1) A wave front runs diagonally through the first medium which has an index of refraction of 1, and when the wave hits boundary transmission occurs and each wave has a different velocity. According to Huygens principle the wave front hits a point and waves are emitted, and the waves in medium 2 are slower because the index of refraction is larger. When all the waves combine it results in a new plane wave, that changes when its moving from medium one to the other. The propagated wave is perpendicular to other wave.
2) When the angle of incidence is adjusted to 10 degrees, it takes the wave longer to hit the other medium.
3) When the wavelength is set to 2 cm more superposition occurs.