Reflection

#Physics
When a wave meets an interface between two mediums of different wave travel speed, reflection of the wave occurs

Topics

$\theta_R=\theta_I$

The angle between the reflected light ray and the normal of the surface is equal to the angle between the incident light ray and the normal of the surface

$\displaystyle E_{0_{R}}=\left\lvert \frac{v_{2}-v_{1}}{v_{2}+v_{1}} \right\rvert E_{0_{I}}=\left\lvert \frac{n_{1}-n_{2}}{n_{1}+n_{2}} \right\rvert E_{0_{I}}$

Reflected wave amplitude
$\displaystyle E_{0_{I}}$ is the incident wave amplitude
$\displaystyle v_{1}$ and $\displaystyle v_{2}$ are the wave velocities in medium 1 (from incident wave) and medium 2 (where the incident wave is heading toward)
$\displaystyle n_{1}$ and $\displaystyle n_{2}$ are refraction indices

$\displaystyle \delta_{R}=\pi(v_{1}>v_{2})+\delta_{I}$

Phase difference in reflected wave compared to incident wave is $\displaystyle \pi$ if the waves travel quicker in the first medium compared to the second, 0 otherwise
I.e. the reflected wave will be upside down relative to the incident wave if waves travel quicker in the first medium