Derivation Level 2 (suitable for students)Double-Slit Formula Here we derive the double-slit formula, which you can use, for example, to find the wavelength of light using a double-slit experiment.
FormulaRayleigh Criterion (Angle, Distance, Wavelength) $$ d_{\text{min}} ~=~ 0.61 \,\cdot\, \frac{\lambda}{n \, \sin(\varphi)} $$
FormulaTotal Internal Reflection (Critical Angle, Refractive Index) $$ \alpha_{\text c} ~=~ \arcsin\left( \frac{n_2}{n_1} \right) $$
FormulaSnell's Law (Angle of Incidence and Refraction, Refractive Index) $$ n_1 \, \sin(\alpha_1) ~=~ \sin(\alpha_2) \, n_2 $$
LessonLevel 3 (up to Physics B.Sc.)Linearly and Circularly Polarized Electromagnetic Waves Here you will learn about polarized light, i.e. linearly or circularly polarized electromagnetic waves, and what characterizes them.
FormulaPhase Velocity of a Wave (Wavelength, Period) $$ \class{blue}{ v_{\text p} } ~=~ \frac{ \class{red}{ \lambda } }{ T } $$
FormulaBiconcave Lens (Focal Length, Refractive Index, Radius of Curvature) $$ \frac{1}{f} ~=~ \frac{n_{\text L} - n_{\text M}}{n_{\text M}} \, \left( \frac{1}{R_1} - \frac{1}{R_2} \right) $$