Free space is the most simple and elementary electromagnetic medium. A medium is the stuff that waves propagate through. The properties, permittivity and permeability, define how electromagnetic waves travel through a medium. Also, the medium has an intrinsic impedance: This article is in need of attention. ... Permeability has several meanings: In electromagnetism, permeability is the degree of magnetisation of a material in response to a magnetic field. ...
where μ is the permeability of the medium and is the permittivity of the medium.
Waves propagate through a medium with velocity of cw. Simply the propagation velocity of a wave in a given medium is just the wavelength multiplied by its frequency, or its the angular frequency divided by the wavenumber(physics) or phase constant(electrical engineering).
The propagation velocity of electromagnetic waves in free space (medium) is
where, is the vacuum permittivity of free space
is the vacuum permeability of free space.
See also: Electromagnetic spectrum, Electromagnetic radiation, Optics. The electromagnetic spectrum encompasses all possible wavelengths of electromagnetic radiation. ... Electromagnetic radiation or EM radiation is a combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave, effectively transporting energy and momentum. ... See also list of optical topics. ...
In geometrical optics the wave theory of light is ignored and rays are traced through an optical system by applying the laws of reflection and refraction.
If a light ray that is traveling through one homogeneous medium is incident on the surface of a second homogeneous medium, part of the light is reflected and part may enter the second medium as the refracted ray and may or may not undergo absorption in the second medium.
If the surface of the second medium is smooth or polished, it may act as a mirror and produce a reflected image.
If a ray is incident obliquely, then a ray entering a medium with a higher refractive index is bent toward the normal, and a ray entering a medium of lower refractive index is deviated away from the normal.
To an observer in a less dense medium such as air, an object in a denser medium appears to lie closer to the boundary than is the actual case.
If rays parallel to the optic axis are incident on a spherical surface, they are reflected or refracted so that they intersect or appear to intersect at a point on the optic axis.
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