A measure of the flatness of an ellipse, equal to the distance between the two foci divided by the length of the major axis. A field extending outward in all directions from a charged particle, such as a proton or an electron.
Photons travel through space at the speed of light.
When the changes of energy are small, streams of photons can be described as waves of changing electric and magnetic fields, called electromagnetic waves. The most familiar type of electromagnetic radiation is visible light, but the full spectrum of electromagnetic radiation includes radio, microwave, infrared, ultraviolet, X rays and gamma rays. The entire range of electromagnetic waves, named in order of increasing frequency or energy, ranges from radio waves, to microwave, to infrared, to visible or optical, to ultraviolet, to X rays, to gamma rays. The pressure produced by the resistance of electrons to compression once they are squeezed to the point of contact. The number of protons in the nucleus of the atom determines which element it represents.