Security

Security is the condition of being sheltered against danger or loss. In the general sense, security is a perception similar to safety. The nuance between the two is an added emphasis on being protected from dangers that initiate from outside. Individuals or actions that encroach upon the condition of protection are responsible for the breach of security.
The word security in general procedure is synonymous with safety, but as a technical term security means that something not only is protected but that it has been secured. A condition that results from the establishment and maintenance of protective measures that ensures a state of inviolability from hostile acts or influences. With respect to classified matter, the condition that prevents unauthorized persons from having right to use to official information that is safeguarded in the benefit of national security.

Light

Light is electromagnetic energy with a wavelength that is observable to the eye or, in a technical or scientific context, the word is sometimes used to mean electromagnetic emission of all wavelengths. The elementary element that defines light is the photon. The three basic properties of lights are Intensity, or alternatively amplitude, which is related to the observation of brightness of the light, Frequency, or alternatively wavelength, perceived by humans as the color of the light, and Polarization, which is only weakly perceptible by humans under ordinary circumstances. Due to its wave–particle duality, light can show properties of both waves and particles. The study of light, known as optics, is an important research area in modern physics.
The first successful quantity of the speed of light in Europe using an earthbound apparatus was carried out by Hippolyte Fizeau in 1849. Fizeau aimed at a beam of light at a mirror several thousand metres away, and placed a rotating cog wheel in the path of the beam from the source to the mirror and back again. At a certain rate of rotary motion, the beam could pass through one gap in the wheel on the way out and the next gap on the way back. Knowing the distance to the mirror, the number of teeth on the wheel, and the rate of rotation, Fizeau calculated the speed of light as 313 000 km/sv