30.11 - Gotchas
A light wave is a transverse wave. Yes. Both of its components, an electric and a magnetic field, oscillate perpendicularly to its direction of
travel.
Radio signals and light waves are fundamentally different. Both are forms of electromagnetic radiation, so we lean toward “no” in response to
this statement. The wavelength and frequency of radio transmissions and light are significantly different, and humans can see light, but not
radio waves, so one could say “yes”. However, both are electromagnetic waves, and both move at the speed of light.
30.12 - Summary
An electromagnetic wave is a traveling wave consisting of mutually perpendicular
electric and magnetic fields that oscillate transversely to the direction of
propagation. Electromagnetic radiation moves at the “speed of light,” or c, which is
299,792,458 m/s in a vacuum. The value 3.00×10^8 m/s is often used.
Every electromagnetic wave has a characteristic frequency and wavelength. The
electromagnetic spectrum is an ordering of electromagnetic radiation in accordance
with these two properties and extends far beyond the tiny gamut called visible light
that we can detect with our eyes. Some other kinds of electromagnetic radiation are radio waves (AM and FM), television signals, microwaves,
infrared light, ultraviolet light, x-rays, and gamma rays.
Maxwell proved that the speed of an electromagnetic wave equals the reciprocal of the square root of the product of two fundamental physical
constants, the electric permittivity of free space İ 0 , and the magnetic permeability of free space μ 0. This value turned out to be equal to the
empirically well-measured speed of light, providing strong evidence that light is a form of electromagnetic radiation.
Linearly polarized light consists of light waves whose electric fields all oscillate in the same plane. This type of light can be created by several
methods, such as by passing unpolarized light, whose electric fields oscillate in many directions, through a polarizing filter. The direction of
polarization that results is called the transmission axis of the filter. As a randomly polarized wave passes through such a filter, only the
component of its oscillating electric field that is aligned with the transmission axis passes through.
The scattering of light passing through a transparent substance is the absorption and re-emission of light waves of characteristic frequencies
by atoms in the substance. Scattering in the atmosphere is responsible for the blue glow of the sky, the yellowish hue of the Sun, and the red
color of sunsets.
Optical activity forms the technological basis of the liquid crystal displays (LCDs) used in many consumer electronic devices.
Proportionality of fields