Fundamentals of photonics

• Snell's law states that when a wavefront passes from one medium into another, it changes direction at the boundary between them according to Snell's Law (n1 sinθ1 = n2 sinθ2).
• The refractive index is the ratio of the speed of light in vacuum to its speed in a medium.
• Total internal reflection occurs when the angle of incidence exceeds the critical angle, causing all reflected rays to be parallel to the interface.
• Refraction can cause dispersion, where different wavelengths are bent differently due to their different speeds in the material.
• A prism separates white light into different colors due to dispersion caused by differences in refraction indices for different wavelengths.
• Dispersion can also occur within an optical fiber, leading to chromatic dispersion if the difference in propagation times for different wavelengths becomes significant.
• Polarization refers to the orientation of electric field vectors in electromagnetic waves.
• fermat’s principle says light travel along the path of least time
• Hero’s principle says light travels the minimum distance
• Parallel rays in spherical mirrors meet at diferent points - this envelope curve is called caustic curve
• Rays that make small angles with the mirror’s axis are called paraxial rays.
• In the paraxial approximation, where only paraxial rays are considered, spherical mirrors have a focusing property like elliptical mirror
• Reflectance at normal incidence is ((n1 - n2)/(n1+n2)) ^ 2
• Reflection coefficient r=((n1-n2)/(n1+n2))
• Reflectance is equal to the square of reflection coefficient