Spectral flux of radiation. Point radiation source

A characteristic of the radiation spectrum equal to the ratio of the intensity (flux density) of radiation in a narrow frequency interval to the value of this interval. Is the application of the concept of power spectral density to electromagnetic radiation. The energy of the light beam is unevenly distributed over waves of different lengths. The dependence of frequency on wavelength is described as λv=c

To characterize the frequency distribution of radiation, the intensity per unit frequency interval is used. This quantity is called the spectral density of radiation intensity and is denoted as I(v).

Integral radiation- this is radiation corresponding to the entire spectrum of frequencies (wavelengths) ranging from zero to infinity.

89) Define the concepts: flux and flux density of spectral radiation: flux and flux density of integral radiation? Spectral radiation density- characteristic of the radiation spectrum, equal to the ratio of the intensity (flux density) of radiation in a narrow frequency interval to the value of this interval. Is the application of the concept of power spectral density to electromagnetic radiation.

The integral radiant flux emitted from a unit surface of a body in all directions of hemispherical space is called integrated radiation density(W/m2)

The total radiation from the surface of a body over all wavelengths of the spectrum is called integral or in full flow radiation Q

94) ABSORPTION CAPACITY

body - the ratio of what is absorbed by the body radiation flux to the monochromatic falling on it. frequency radiation flux v; same as monochromatic absorption coefficient. P.S. depends on the substance of which the body consists, on the shape of the body and on its temperature. If P. s. body in a certain frequency range temperature p is equal to 1, they say that under these conditions it is absolutely black body. absorption capacity along with spectral emissivity included in Kirchhoff's radiation law and characterizes the deviation of absorbing properties given body from the properties of an absolutely black body. P.S. – the most important characteristic thermal radiation. Amount P. s., transmittance coefficient And reflection coefficient body is 1

Body permeability.

This value characterizes the share of thermal energy flow

radiation transmitted by the body d Ф prop depending on the magnitude of the incident

energy flow d Ф falls and is determined as follows:

d (λ , T) = . (1.4)

This value characterizes the intensity of the fishing process

processing by object depth.

REFLECTIVITY- a quantity characterizing the ability of the surface of a body or the interface between two media to reflect the electric-magnetic flux incident on it. radiation or elastic waves. Quantities, characteristics of O. s. - coefficient reflections. O. s. depends on the angle of incidence and polarization of the incident electric magnet. radiation. Dependence O. s. surface on the wavelength of radiation in the area visible light is perceived by the human eye as the color of a reflective surface.

96) Absolutely black body- a physical idealization used in thermodynamics, a body that absorbs all electromagnetic radiation incident on it in all ranges and does not reflect anything. Despite the name, a completely black body itself can emit electromagnetic radiation of any frequency and visually have color. The radiation spectrum of an absolutely black body is determined only by its temperature.

The Importance of the Blackbody in Spectrum Questions thermal radiation of any (gray and colored) bodies in general, in addition to the fact that it represents the simplest non-trivial case, it also consists in the fact that the question of the spectrum of equilibrium thermal radiation of bodies of any color and reflection coefficient is reduced by the methods of classical thermodynamics to the question of the radiation of absolutely black (and historically this has already been done by end of the 19th century century, when the problem of black body radiation came to the fore).

Laws describing radiation: 1st 2nd Wien's laws, Rayleigh-Jeans Law, Planck's Law, Stefan-Boltzmann Law, Wien's Displacement Law

97) Not sure if this is correct!!!

99 . Define the concept “Spectral degree of blackness”. How does it change in real life? tel when changing wavelength (for example Me and refractories)?

Spectral degree of emissivity is a coefficient connecting the spectral densities of the fluxes of a given body’s own radiation and an absolutely black body at the same temperatures (OR the ratio of the radiation energy of a body at a given wavelength to the radiation energy of an absolutely black body at the same wavelength at the same temperature).

In the region of wavelengths characteristic of thermal radiation, the unoxidized surface of the metal is characterized by a continuous decrease, and the dielectric surface (refractories) is characterized by an increase in the spectral degree of emissivity with increasing wavelength.

100 . What is the Integral degree of blackness, how to use it. determine the flux density of its own radiation?

The integral degree of blackness characterizes the intensity of the body’s own radiation over the entire wavelength range (OR the ratio of the total energy emitted over the entire wavelength range to the total radiation energy of an absolutely black body at the same temperature).

Self-radiation flux density (according to the Stefan-Boltzmann law):

q SOB =ε σ 0 T 4 , where

T-absolute body temperature, K

σ 0 – Stefan-Boltzmann constant

102 . For what purpose was the gray body model created? What is different about gray body radiation compared to a real body?

Gray body - a body whose absorption coefficient is less than 1 and does not depend on the radiation wavelength

Created to facilitate calculations of radiation t/exchange in real systems as an approximation to the description of radiation real bodies.

For real bodies, the degree of emissivity depends on the wavelength, and for gray bodies the degree of emissivity does not depend on either t or the wavelength and is constant.

103 What is greater, the flux of effective radiation or the flux of intrinsic radiation, and in which case are these fluxes equal?

Effective radiation flux is the sum of the own radiation of other bodies and the radiation reflected by these bodies in the process of radiative heat exchange:

Q EF = Q SOB + Q OTR

Those. the effective radiation flux is always greater than the intrinsic radiation flux, except for the case when Q OTP =0

106 List the main properties of angular coefficients.

Property of closure

Property of reciprocity

Property of non-concave: the angular coefficient of radiation from a certain surface to itself for non-concave surfaces is zero

108 . What are the features of the radiation of a gaseous medium in comparison with solid and liquid bodies and how does this affect the determination of the flux of the gas’s own radiation?

Peculiarities:

No continuous radiation

Gaseous bodies emit only a certain spectrum of waves - spectral radiation

Each gas has its own spectrum.

109 Define the resulting radiation flux. How is it expressed through the flux of incident radiation, and how – through the flux of its own radiation?

The resulting radiation flux is the difference between the fluxes of absorbed and intrinsic radiation:

For an opaque body (at R=1-A), the expression for the resulting radiation flux is valid:

110 . Features of radiation and absorption of radiant energy by gases. Determination of their optical properties.

The emission spectrum of gases is linear. Gases do not emit rays of all wavelengths. Such radiation is called selective.

111 Transfer of radiant energy in emitted and absorbed media.

113 .Calculation of radiative heat transfer in a system with a radiating and absorbing medium.

The zonal method of α environment is used for calculations: 1-gas volume, 2-closed. surface, limiting gasV

Effective radiation from the axis of surfaces is diffusion.

The calculation is carried out in 2 stages:

Effective radiation fluxes are determined for all zones

Based on the found values ​​of effective fluxes, for surface zones we find the fluxes of the resulting radiation, and for volumetric zones we determine temperatures

Electromagnetic waves transfer energy from one area of ​​space to another. Energy transfer occurs along rays - imaginary lines indicating the direction of wave propagation. The most important energy characteristics electromagnetic waves is the radiation flux density. Let's imagine a platform of area S located perpendicular to the rays. Let us assume that during time t the wave transfers energy W through this area. In other words, the radiation flux density is the energy transferred through a unit area (perpendicular to the rays) per unit time; or, which is the same thing, is the radiation power transferred through a single area. The unit of measurement for radiation flux density is W/m2. The radiation flux density is related by a simple relationship with the electrical energy density magnetic field. We fix the area S, perpendicular to the rays, and a short period of time t. Energy will pass through the area: W = ISt. This energy will be concentrated in a cylinder with base area S and height ct, where c is the speed of the electromagnetic wave. The volume of this cylinder is equal to: V = Sct. Therefore, if w is the energy density electromagnetic field, then for the energy W we also obtain: W = wV = wSct. Equating the right-hand sides of the formulas and and reducing by St, we obtain the relation: I = wc. The radiation flux density characterizes, in particular, the degree of influence of electromagnetic radiation on its receivers; When they talk about the intensity of electromagnetic waves, they mean the radiation flux density. An interesting question is how the intensity of radiation depends on its frequency. Let an electromagnetic wave be emitted by a charge making harmonic vibrations along the X axis according to the law x = x0 sin iet. The cyclic frequency w of charge oscillations will at the same time be the cyclic frequency of the emitted electromagnetic wave. For the speed and acceleration of the charge we have: v = X = x0ш cos Шt and a = v = -x0Ш2 sin Шt. As we see, a ~ w2. Tension electric field and the magnetic field induction in an electromagnetic wave are proportional to the acceleration of the charge: E ~ a and B ~ a. Therefore, E ~ w2 and B ~ w2. The electromagnetic field energy density is the sum of the electric field energy density and the magnetic field energy density: w = wel + wMarH. The energy density of the electric field, as we know, is proportional to the square of the field strength: w^ ~ E2. Similarly, it can be shown that wMarH ~ B2. Consequently, w^ ~ w4 and wMarH ~ w4, so w ~ w4. According to the formula, the radiation flux density is proportional to the energy density: I ~ w. Therefore I ~ wA. We got important result: intensity electromagnetic radiation proportional to the fourth power of its frequency. Another important result is that the radiation intensity decreases with increasing distance from the source. This is understandable: after all, the source radiates in different directions, and as you move away from the source, the emitted energy is distributed over an increasingly larger and larger area. The quantitative dependence of the radiation flux density on the distance to the source is easy to obtain for the so-called point source of radiation. A point source of radiation is a source whose dimensions can be neglected in a given situation. In addition, a point source is assumed to radiate equally in all directions. Of course, a point source is an idealization, but for some problems this idealization works great. For example, when studying the radiation of stars, they can be considered point sources - after all, the distances to the stars are so enormous that their own sizes can be ignored. At a distance r from the source, the emitted energy is uniformly distributed over the surface of a sphere of radius r. The area of ​​the sphere, recall, is S = 4nr2. If the radiation power of our source is P, then during time t energy W = Pt passes through the surface of the sphere. Using the formula, we then obtain: = Pt = P 4 nr2t 4 nr2 Thus, the radiation intensity of a point source is inversely proportional to the distance to it. Types of electromagnetic radiation The spectrum of electromagnetic waves is unusually wide: the wavelength can be measured in thousands of kilometers, or less than a picometer. However, this entire spectrum can be divided into several characteristic wavelength ranges; within each range electromagnetic waves have more or less similar properties and methods of radiation.

Thus, for is executed:

Tue.

where is the radiation energy transferred through the surface over time.

Among light quantities, an analogue of the concept “radiation flux” is the term “luminous flux”. The difference between these quantities is the same as the difference between energy and light quantities in general.

Spectral flux density

If the radiation is non-monochromatic, then in many cases it turns out to be useful to use a quantity such as the spectral flux density of the radiation. Spectral Density radiation flux is the radiation flux per small unit range of the spectrum. The points of the spectrum can be specified by their wavelengths, frequencies, energies of radiation quanta, wave numbers or any other method. If the variable that determines the position of the points of the spectrum is a certain quantity, then the corresponding spectral radiation flux density is denoted as and is defined as the ratio of the value per small spectral interval enclosed between and to the width of this interval:

Accordingly, in the case of using wavelengths for the spectral radiation flux density, the following will be true:

and when using frequency -

It should be borne in mind that the values ​​of the spectral radiation flux density at the same point in the spectrum, obtained using different spectral coordinates, do not coincide with each other. That is, for example, It is not difficult to show that, taking into account

And

the correct ratio takes the form:

see also

Notes

Wikimedia Foundation. 2010.

• Flow of execution
• Magnetic flux

See what “Radiation Flux” is in other dictionaries:

RADIATION FLOW- (radiant flux), the average radiation power over a time significantly longer than the oscillation period; characterized by the amount of energy transferred by electricity. mag. waves per unit time through k.l. surface. The size of P. and. measured by its effect on... Physical encyclopedia

radiation flux- (Fe[P]) Radiation power, determined by the ratio of the energy transferred by radiation to the transfer time, significantly exceeding the period electromagnetic vibrations. [GOST 7601 78] radiation flux (Fe, P) [GOST 7601 78] [GOST 26148 84] flux... ... Technical Translator's Guide

RADIATION FLOW- (radiant flux radiation power), total energy, transferred by light per unit time through a given surface. The concept of radiation flux (applicable to time periods significantly exceeding the periods of light fluctuations ... Big encyclopedic Dictionary

RADIATION FLOW- the number of particles or quanta penetrating into the elementary sphere per unit time. Usually P. and. are referred to 1 second and its unit is determined accordingly: second minus the first power. If we consider not the number of particles or quanta, but... ... Russian encyclopedia on labor protection

radiation flux- (radiant flux, radiation power), the total energy transferred by light per unit time through a given surface. The concept of radiation flux is applicable to periods of time significantly exceeding the periods of light oscillations. * * * FLOW… … encyclopedic Dictionary

radiation flux- , radiant flux, radiation power, total energy transferred optical radiation(all its frequencies) per unit time through a given surface. For an absorbing surface, the radiation flux is the sum of absorbed and reflected energy... Encyclopedic Dictionary of Metallurgy

radiation flux- spinduliuotės srautas statusas T sritis Standartizacija ir metrologija apibrėžtis Energijos kiekis, kurį elektromagnetinė banga perneša per vienetinį laiko tarpą per tam tikrą paviršių. atitikmenys: engl. flux of radiation; radiant flux; radiant... ...

radiation flux- spinduliuotės srautas statusas T sritis Standartizacija ir metrologija apibrėžtis Išskiriamos, perduodamos arba gaunamos spinduliuotės galia. Matavimo vienetas – vatas (W). atitikmenys: engl. flux of radiation; radiant flux; radiant power;… … Penkiakalbis aiškinamasis metrologijos terminų žodynas

radiation flux- spinduliuotės srautas statusas T sritis Standartizacija ir metrologija apibrėžtis Išspinduliuotų, perduodamų arba priimamų elektromagnetinių bangų galia. atitikmenys: engl. flux of radiation; radiant flux; radiant power; radiation flux vok.… … Penkiakalbis aiškinamasis metrologijos terminų žodynas

radiation flux- spinduliuotės srautas statusas T sritis fizika atitikmenys: engl. flux of radiation; radiant flux; radiation flux vok. Strahlungsfluß, m rus. radiant flux, m; radiation flux, m pranc. flux de radiation, m; flux de rayonnement, m … Fizikos terminų žodynas

Books

• The flow of solar energy and its changes. The book examines and summarizes modern data on the flux of solar radiation in various areas spectrum according to measurements from the Earth and from spacecraft. Much attention paid to errors... Buy for 1300 rubles
• Energy spectrum of particles with energy more than 10 eV and the flux of electromagnetic flares in the surface layer, V. F. Sokurov. In the monograph, the energy spectrum of particles with energies of 10.5-1017 eV was measured using a direct method using a flux of Cherenkov flares with a radiation density of 17-1480 photons cm 2 eV. A break in the spectrum was obtained...

GHS Notes Radiation flux $\backslash Phi\_e$ - physical quantity, one of the energy photometric quantities. Characterizes the power transferred by optical radiation through any surface. Equal to ratio energy transferred by radiation through a surface to the time of transfer. It is understood that the duration of the transfer is chosen so that it significantly exceeds the period of electromagnetic oscillations. The designation used is $\backslash Phi\_e$ or $P$ .

Thus, for $\backslash Phi\_e$ performed:

$\backslash Phi\_e=\backslash frac(dQ\_e)(dt),$ Tue.

Where $dQ\_e$- radiation energy transferred through the surface over time $dt$.

Among light quantities, an analogue of the concept “radiation flux” is the term “luminous flux”. The difference between these quantities is the same as the difference between energy and light quantities in general.

Spectral flux density

If the radiation is non-monochromatic, then in many cases it turns out to be useful to use a quantity such as the spectral flux density of the radiation. Spectral radiation flux density is the radiation flux per small unit range of the spectrum. The points of the spectrum can be specified by their wavelengths, frequencies, energies of radiation quanta, wave numbers or any other method. If the variable that determines the position of the points of the spectrum is a certain quantity $x$, then the corresponding spectral radiation flux density is denoted as $\backslash Phi\_(e,x)$ and is defined as the ratio of the quantity $d\; \backslash Phi\; \_e(x),$ falling on a small spectral interval concluded between $x$ And $x+dx,$ to the width of this interval:

$\backslash Phi\_(e,x)(x)=\backslash frac(d\backslash Phi\_e(x))(dx).$

Accordingly, in the case of using wavelengths for the spectral radiation flux density, the following will be true:

$\backslash Phi\_(e,\backslash lambda)(\backslash lambda)=\backslash frac(d\backslash Phi\_e(\backslash lambda))(d\backslash lambda),$

and when using frequency -

$\backslash Phi\_(e,\backslash nu)(\backslash nu)=\backslash frac(d\backslash Phi\_e(\backslash nu))(d\backslash nu).$

It should be borne in mind that the values ​​of the spectral radiation flux density at the same point in the spectrum, obtained using different spectral coordinates, do not coincide with each other. That is, for example, $\backslash Phi\_(e,\backslash nu)(\backslash nu)\backslash ne\backslash Phi\_(e,\backslash lambda)(\backslash lambda).$ It is easy to show that, taking into account

$\backslash Phi\_(e,\backslash nu)(\backslash nu)=\backslash frac(d\backslash Phi\_e(\backslash nu))(d\backslash nu)=\backslash frac(d\backslash lambda)(d\backslash nu)\backslash frac(d\backslash Phi\_e(\backslash \; lambda))(d\backslash lambda)$ And $\backslash lambda=\backslash frac(c)(\backslash nu)$

the correct ratio takes the form:

$\backslash Phi\_(e,\backslash nu)(\backslash nu)=\backslash frac(\backslash lambda^2)(c)\backslash Phi\_(e,\backslash lambda)(\backslash lambda).$

see also

Write a review about the article "Radiation Flux"

Notes

An excerpt characterizing the Flow of Radiation

In the Russian army, as they retreat, the spirit of bitterness against the enemy flares up more and more: retreating back, it concentrates and grows. There is a clash near Borodino. Neither army disintegrates, but Russian army immediately after the collision, it retreats just as necessarily as a ball necessarily rolls away when it collides with another ball rushing towards it with greater speed; and just as inevitably (although having lost all its strength in the collision) the rapidly scattering ball of invasion rolls over some more space.
The Russians retreat one hundred and twenty versts - beyond Moscow, the French reach Moscow and stop there. For five weeks after this there is not a single battle. The French don't move. Like a mortally wounded animal, which, bleeding, licks its wounds, they remain in Moscow for five weeks, doing nothing, and suddenly, without any new reason, they run back: they rush onto the Kaluga road (and after the victory, since again the battlefield remained behind them at Maloyaroslavets), without entering into a single serious battle, they run even faster back to Smolensk, beyond Smolensk, beyond Vilna, beyond the Berezina and beyond .
On the evening of August 26, both Kutuzov and the entire Russian army were sure that battle of Borodino won. Kutuzov wrote to the sovereign in this way. Kutuzov ordered to prepare for new fight, in order to finish off the enemy, not because he wanted to deceive anyone, but because he knew that the enemy was defeated, just as each of the participants in the battle knew it.
But that same evening and the next day, news began to arrive, one after another, about unheard-of losses, about the loss of half the army, and a new battle turned out to be physically impossible.
It was impossible to give battle when information had not yet been collected, the wounded had not been removed, shells had not been replenished, the dead had not been counted, new commanders had not been appointed to replace the dead, people had not eaten or slept.
And at the same time, immediately after the battle, the next morning, French army(by that rapid force of movement, now increased as if by inversely squares of distance) was already approaching the Russian army by itself. Kutuzov wanted to attack the next day, and the whole army wanted this. But in order to attack, the desire to do so is not enough; there needs to be an opportunity to do this, but this opportunity was not there. It was impossible not to retreat to one transition, then in the same way it was impossible not to retreat to another and a third transition, and finally on September 1, when the army approached Moscow, despite all the strength of the rising feeling in the ranks of the troops, the force of things demanded so that these troops march for Moscow. And the troops retreated one more, to the last crossing and gave Moscow to the enemy.
For those people who are accustomed to thinking that plans for wars and battles are drawn up by commanders in the same way as each of us, sitting in his office over a map, makes considerations about how and how he would manage such and such a battle, questions arise as to why Kutuzov didn’t do this and that when retreating, why he didn’t take up a position before Fili, why he didn’t immediately retreat to the Kaluga road, left Moscow, etc. People who are used to thinking like this forget or don’t know those inevitable conditions in which the activities of every commander in chief always take place. The activity of a commander does not have the slightest resemblance to the activity that we imagine while sitting freely in an office, analyzing some campaign on a map with known quantity troops, from one side and the other, and in a certain area, and starting our considerations from some certain moment. The commander-in-chief is never in those conditions of the beginning of some event in which we always consider the event. The commander-in-chief is always in the middle of a moving series of events, and so that never, at any moment, is he able to think through the full significance of the event taking place. The event is imperceptibly, moment by moment, carved into its meaning, and at every moment of this sequential, continuous carving of the event, the commander-in-chief is at the center the most difficult game, intrigues, worries, dependence, power, projects, advice, threats, deceptions, he is constantly in the need to answer countless questions offered to him, always contradicting one another.

The radiation flux density can vary along certain radiation directions. The amount of energy emitted in the direction /, determined by the angle ty with the normal to the surface n (Fig. 16.1) per unit elementary area per unit time within a unit elementary solid angle 4o, is called the angular radiation density.

The radiation flux density can vary along certain radiation directions. The amount of energy emitted in a certain direction /, determined by the angle r ] with the normal to the surface n (Fig. 16 - 1) unit of an elementary area per unit of time within the elementary solid angle do, is called the angular density of radiation.

The radiation flux density is proportional to the fourth power of frequency.

Radiation flux density E is an integral characteristic relating to the entire wavelength range. Spectral radiation flux density EI dE / dhB characterizes the distribution of radiation energy over wavelengths.

The density of the radiation flux incident on the screen, E (illumination intensity or simply illumination) changes due to the deflection of the rays.

The radiation flux density is determined by the direct and reflected fluxes. The magnitude of the reflected flux depends on the distance between the source and the reflecting surfaces.

Radiation flux density is the amount of radiation energy passing per unit time through a unit surface area within a hemispherical solid angle.

The radiation flux density depends on the angle of incidence of waves on the surface of the body, since with increasing angle of incidence the same radiation flux is distributed over an increasingly larger surface.

The radiation flux density of a gas as a whole is the sum of the radiation flux densities of all bands of its spectrum.

The radiation flux density of a laser beam is characterized by the ratio of the total output power to the area of ​​the heating spot at the focus. An increase in the flux density to 105 - 106 W/cm2 and its distribution over a heating spot with a diameter of 0 25 - 0 5 mm leads to the formation of a narrow channel in the liquid phase, through which radiation penetrates deep into the volume of the material being cut. The presence of this phase in destruction products is a feature of laser processing of metals. It seems quite complex and must be built taking into account thermal and hydrodynamic phenomena.

Efo - radiation flux density corresponding to the angle φ; dQ is the elementary solid angle at which an elementary area on the surface of a hemisphere having a center at this point is visible from a given point of the radiating body; f is the angle between the normal to the radiating surface and the direction of radiation. For real bodies, Lambert's law is satisfied only approximately.

Fnat is the flux density of leakage radiation that reaches the detection point after passing at least part of its initial path through the protection. This consideration does not take into account particles or quanta, the scattering trajectory of which can be conventionally designated as follows: source - filler - protection - filler - detector. This means that the protection material can be considered a completely black body for radiation entering it from the filler.

The concept of radiation flux density is not associated with any idea of ​​the direction of radiation, as a result of which this quantity is intended to characterize equally bright emitters in any direction.