Absorption in Physics

In physics, absorption is the process by which the energy of a photon is taken up by another entity, for example, by an atom whose valence electrons make transition between two electronic energy levels. The photon is destroyed in the process. The absorbed energy may be re-emitted as radiant energy or transformed into heat energy. The absorption of light during wave propagation is often called attenuation.

The absorbance of an object quantifies how much light is absorbed by it (not all photons get absorbed; some are reflected or refracted instead). This may be related to other properties of the object through the Beer-Lambert law.

For most substances, the amount of absorption varies with the wavelength of the light, leading to the appearance of color in pigments that absorb some wavelengths but not others. For example, an object that absorbs blue, green and yellow light will appear red when viewed under white light. More precise measurements at many wavelengths allow the identification of a substance via absorption spectroscopy.

The specific phenomena involving absorption of electromagnetic radiation at the Earth's surface have several important aspects. These phenomena include regulating the temperature of the Earth's crust, surface waters and lower atmosphere. Changes in the Earth's crust such as glaciation, deforestation, polar ice melting, will necessarily alter the quantity and wavelength selectivity of electromagnetic absorption at the Earth's surface; correspondingly, changes in climate such as global warming may accompany changes in electromagnetic absorption or its inverse, the albedo. Regulation of the temperature of surface waters has been analyzed with respect to the influence of electromagnetic radiation absorption, indicating the effects of total solar insolation and the local albedo.

Absorption refers to the absorption of sound waves by a material. The absorption is the "missing piece", when comparing the total reflected and transmitted energy with the incident energy.

It is the property of a material that changes acoustic energy into usually heat energy. A material or surface that absorbs sound waves does not reflect them. Absorption of a given material is frequency dependent as well as being affected by the size, shape, location, and mounting method used.

A good sound absorber is normally a porous material e.g. mineral wool, glass wool, but also Micro perforated plates work as sound absorbers.

Absorption is not a single mechanism of sound attenuation. Propagation through a heterogeneous system is affected by scattering as well.

2.2. Match the words to form collocations:

2.3. Translate the sentences below paying attention to the emphatic constructions.

1. It was only very gradually that the ideas of atoms became advanced and useful.

2. It is the "optical theorem" put in precise form by Niels Bohr that enabled us to compute the total cross section.

3. Again, it was the temperature change that turned out to be sufficient to account for an appreciable part of resistance change while the field was on.

4. It was Heinrich Hertz who in 1887 - 1888 succeeded in showing that rapidly oscillating electric charges do indeed produce electromagnetic waves.

5. Therefore one can conclude that Cygnus X-I docs comprise a black hole. At least this conclusion is the most reasonable cue.

6. Not until mechanics of fluids, mechanics of solids and applied mathematics were sufficiently advanced was ii possible io solve the main problems of fluid mechanics.

7. The first radio noise from outerspace was detected in 1930, but it was not until after the Second World War that a new branch of science, radio astronomy, was developed.

8. Not only did they collect material on the problem but they also arranged it properly.

9. Thus not only docs elastic scattering respond to the overall charge magnetic moment of the neutron but also reveals what is going on inside.

10. Not only did the newly discovered electron provide an entity (сущность, нечто реально существующее) which was assumed to be a constituent of all atoms, but it also provided a natural unit of electricity.

11. Perhaps, never before has been achieved more extensive and complete cooperation among scientists as in this task to prevent war.

12. There is no denying the fact that never before was there any discrepancy in our work between theoretical and experimental data.

13. No sooner had the existence of the electron been established than many phenomena were nicely accounted for.

14. No sooner did the electron flow through the coil cease than the magnetic field collapsed and the iron was no longer magnetized.

15. This circuit will not be suitable for many applications, neither will it greatly facilitate the attainment of the amplified signal.

16. Mercury is not known to have atmosphere, nor is a permanent gaseous envelope expected to occur under the conditions existing on the planet.

17. The history of modern optics is related to two theories of light. Neither concept has been rejected. Nor is there any paradox in the occurrence of both wave and particle theory of light.

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Date: 2015-05-18; view: 654; Нарушение авторских прав