In the previous installment we talked about pulsations, interference must be known, where it shows us that when several waves coincide at the same point in the middle through which they propagate. The vibrations overlap and the state of vibration resulting from the point is the sum of those produced by each wave, which in turn produces oscillations as an additional part of the pulsation phenomenon, but what is unique is that for those who are unaware of this it is just an oscillation to call it that way, it is also a back and forth movement around a central or equilibrium point, under a frequency of time because the variation of a magnitude around a point along it is carried out in a magnitude of time or time interval.

The mathematical equation where a new wave that propagates in the positive direction, which represents a pulse ω in the form of the arithmetic mean of the pulses of two waves, which is superimposed and sharing said frequency:

ѵ = ω / 2π

ѵ = ω1 + ω2 / 2. 1 / 2π the resultant ѵ1 + ѵ2 / 2

For the case of the wavelength we have: λ = 2π / K.

Already knowing the basic fundamentals of the pulsations, let's get into the matter when a wave establishes the separation surface of two media differently, they manage to create two waves, thanks, dear reader, what happens in a simple way that starts from the energy It penetrates the new medium and the rest remains in the first medium, since the wave that passes to the second medium changes the direction of propagation. What originates is a refractory wave and the other when it has an action that does not stop is a reflected wave.

For the case where the surface in S, allows it to separate two different midpoints, with a front of a wave in a flat segment AB, it approaches it, reminding a bit of Huygen's theory, when speaking the wave on the surface, we find that each point will be an emitting center of a secondary wave, well now let's put the case to make the segment AB more singular, so that this in turn forms an angle i, which it will not emit the or it gives either for A to A 'and for the same time from B to B', the singular thing is that a new front A'B 'is generated.

For the case of speeds for AA '= BB' = v.T; since an angle is formed at i, we are left with sin i BB '/ AB' and sin r = AA '/ AB', to analyze the incident ray. Which refers to the normal which is contained in the same plane, since the angle of incidence and reflection are equal.

For the case of refraction, starting from the wave front, it affects an initial speed and then a second speed of the wave that penetrates the second medium, since the propagation speed is lower in the same plane.

sin i / sin r = V1 / V2, with the object that the velocity of the second medium is less than the initial v2 <v1, until reaching the normal.