Black-body radiation
In a dark area a black body at room temperatures appears black because most of the energy radiating on them is in the ultraviolet spectrum and is not to see by the human eye. In 1860 Gustav Kirchhoff introduced the concept black body. Black holes are close to perfectly black objects because they absorb the radio waves hitting them. The radiation emitted can reflect Black-Body Radiation (aka Hawking - radiation), that has a temperature that depends on the mass of the black hole. As its temperature rises it starts becoming reddish orange yellow, white and ultimately blue-white. In high lighting conditions the human eye can not detect color for short periods of time.
Black body
The ideal body which emits and absorbs all frequencies, are reffered as black body. The radiation emitted by black body is often called as Black Body Radiation. According to Electromagnetic theory, the energy emitted or absorbed continuously, thus electromagnetic radiation is proportional to the intensity i.e, square of amplitude.
And it is independent of its frequency or wavelengths.
Counting standing waves is Rayleigh’s sound idea
Rayleigh waves are a type of surface wave that travel near the solid surfaces. These waves includes both longitudinal and transverse motion, that decrease exponentially in amplitude as distance from the surface increases. At greater depths the particle motion becomes prograde. Rayleigh has done a natural approach. His discovery was done a few months before Planck discovery. Lord Rayleigh took direct approach to the radiation inside the oven, he just considered the radiation to be the collection of standing waves in a cubical enclosure. These standing electromagnetic were crystal clear. A quarter century earlier, he solved the identical problems. The task was to search and catalogue the various standing waves in a room. In room, the amplitude of the sound waves goes up to zero at walls. But the condition is that wall must be a perfect conductor.
How is radiation used?
There are various uses of Radiation. Irrespective of nuclear power and nuclear weaponry, there remains a wide array of ways in which radioactive material and the radiation it gives off remain useful in the daily lives of people all over the world.
It is used as :
- SMOKE DETECTORS
- MEDICINE
- RADIOGRAPHY
- FOOD SAFETY
