The light travels through water and gets reflected off on the glass surface into the water. There had been a 180° phase change between the incident and the reflected wave. This is called Total internal reflection (TIR).
In total internal reflection, in physics, a ray of light in a medium such as water or glass is completely reflected back into the medium from the surrounding surfaces. This phenomenon occurs when the angle of incidence is greater than a certain critical angle called the critical angle.
TIR only occurs when both of the following two conditions are met
Thus, the phases which include the TIR are the incident and the reflected phase and the incident light hits the surface while the reflected light reflects back.
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