The light that is emitted by the sun or light bulb is not coherent. It shines in different directions and shows different wavelengths. The entire spectrum of the visible light is covered. It is very different with coherent light, which only shines in a particularly “synchronized” way in a wavelength (light colour). In the following there should be a brief explanation.
What is coherent light?
Coherent light is electromagnetic radiation that has a certain wavelength. So it is always a single -colour light, since the wavelength determines the colour. In addition, the waves are “synchronized”, i.e. they shine in the same direction, they swing in the same level and in the same phase. All descriptive parameters (frequency, polarization and phase) are in a fixed spatial and temporal context, so that they Reinforce electromagnetic waves by overlapping. The word coherent is used as an abbreviation for this connection. If you refer to only one of the connections, one speaks of time (frequency and phase) or spatial coherence (polarization).
How does coherent light arise?
It is not possible to create coherent light with a light source alone. This requires further aids such as grids, prisms or columns.
Temporal and spatial coherence are the most important features of coherent light. Time coherence means that the phase relationships between two wave trains do not change over a longer period of time, but always remain constant. There are no phase shifts, even with a spatial coherence. It is best to find out when you look at the wave spatially. This condition remains until there is a change that requires the effects of external influences.
How does coherent light arise? The most important prerequisite is that there are columns, prisms, grids or mirrors on which the light can hit from a certain light source. This process can be realized with the light of the sun and the light of a light bulb. If the light meets the obstacle, it is first divided and then brought back to overlay.
What is coherent light required for?
The laser radiates coherent light. This is very important because they would not work otherwise. This light is particularly effective and can be focused very finely. The uniformity and the high energy density can be used for various purposes. In addition to the There are numerous other possible uses of the coherent light. This includes spectroscopy and interferometry. Practical applications can be found in signal processing and quantum cryptography, but also in material processing. Furthermore, coherent light sources are indispensable when creating holograms.
Why is coherent light on the double gap?
The double gap is an excellent tool to produce coherent light. If the light comes through a double gap, it is immediately shared. Then the two parts overlap, which results in bending on each gap. Now the light can spread semicircularly. It overlaps wherever two wave mountains or two wave valleys meet. The consequence of this is that there will be reinforcements. In contrast, there are places where a wave crest meets a wave valley, which results in a deployment.
Why is a laser coherent?
At a laser the light is reinforced by the laser effect. Laser stands for “Light Amplification by Stimulated Emission of Radiation”. The effect describes that an excited electron sends out a photon when it is stimulated by another, flying photon. The wavelength, direction and polarization is taken over by the original photon. Accordingly, all prerequisites for coherence are given.
In the laser, this situation is deliberately brought about by reflecting light between two mirrors back and forth that more and more stimulated photons are emitted.
Conclusion on the coherence of light
Light coherence is a factor that has outstanding importance in laser look and in many other areas. If the laser light were not coherent, its effect would not be so intense, and it could not perform its intended task. Coherent light must always be created artificially, because it doesn't happen in nature. The sunlight and the light of a light bulb are not coherent, but incoherent. This means that it covers a wide range of electromagnetic waves. In contrast, coherent light only consists of a very specific wavelength. For example, it can be generated with a double gap, a grid or a mirror.
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