Optics and Electromagnetic Wave Applications
Ever wondered how your internet travels through cables at lightning speed? Fibre optic cables use total internal reflection to transmit data using light waves. When light hits the boundary between two materials at an angle greater than the critical angle, it reflects completely back instead of passing through.
The refractive index tells you how much light slows down in a material compared to air. Using the formula n = sin θc (where θc is the critical angle), you can calculate that a material with a critical angle of 43.8° has a refractive index of approximately 1.45. Light travels slower in denser materials - if the refractive index is 1.48, light speed becomes 3×10⁸ ÷ 1.48 = 2.03×10⁸ m/s.
Fibre optic cables have three main layers: the core (carries light), cladding (reflects light back), and protective outer jacket. Multimode fibres allow multiple light paths, whilst single mode fibres use just one path for clearer signals over longer distances.
Key Tip: Remember N=CV means refractive index equals speed of light in vacuum divided by speed of light in the material.
Modern communication relies on electromagnetic waves - satellites use microwaves, mobile phones use radio waves, and infrared controls your TV remote. The inverse square law shows that wave intensity decreases rapidly with distance, which is why your phone signal gets weaker further from towers.
