Introduction to astrophysics

Abstract

The most important carrier of information from all kinds of heavenly bodies is light. Light is an electromagnetic wave which is characterized by an electric field E and magnetic field H, and the direction of its propagation is at right angles to both these fields. Unlike mechanical waves, e.g. sound waves on the ocean, it can propagate through empty space. So, if Z-direction is the direction of its propagation (Fig. 1.1), then Y and X directions are the directions of electric and magnetic fields. The wave motion can be described by a sine curve and the distance between two consecutive peaks measures the wavelength λ, which is an important characterization of the propagating light.