# Write a 16 pages paper on electromagnetic radiation. Both electric and magnetic fields in an electromagnetic wave are variable in time

Write a 16 pages paper on electromagnetic radiation. Both electric and magnetic fields in an electromagnetic wave are variable in time. Maxwell’s equation says that any electromagnetic wave has a velocity propagation called c. Nowadays, we know that the speed of light in a vacuum has a value near to 300,000 km/s. The speed of light in any other medium is less than in the vacuum. Physics tell us that the light has energy flux given by the Poynting vector, then it has momentum. Furthermore, the light has radiation pressure. The plane wave model of Maxwell’s equation is a trivial solution, however, there exist other models such as spherical waves. An electromagnetic wave is described also by its wavelength. this is related to its period T and its speed, c.

The human eye is sensitive to the Sun’s light this is due to man evolution. The human has invented instruments able to detect almost any electromagnetic radiation coming from deep Universe, in fact, it is coming from anywhere. Additionally, the man has designed observational methods able to increase the quality of surveys.

The optical telescope works best in the visible part of the electromagnetic spectrum. The visible window is around between 7000 A and 4 000 A. The radio astronomer uses huge radio dish antennas, these instruments work best at large electromagnetic wavelength, i.e. &gt. 109 A. When the radiation is between 109 and 106 A the astronomers use bolometers in order to detect the millimeter/submillimetre-wavelength. At infrared level between 106A and 7000 A, they use CCD detectors at very low temperatures. In order to detect ultraviolet waves i.e. between 4000A and 10A, the astronomers use solid-state devices. The X-Rays between 10A – 0.1A the detection is given by collision between particles. The most energetic particles are called Gamma rays it has &lt. 0.1 A, thus the detection is using external electromagnetic fields i.e. Lorentz force.