Blackbody Radiation Theory Research Articles

Visible characteristics of space-based targets based on bidirectional reflection distribution function

A precise modeling method of visible characteristics of the space-based target was presented based on bidirectional reflection distribution function (BRDF). The background characteristics of the space-based target were represented to build models of direct solar radiation and reflected radiation of the Earth based on blackbody radiation theory. The geometry characteristics of the target were analyzed to establish a surface equation of each surface based on its body coordinate system. The material characteristics of the target surface were described by introducing a BRDF model which considers the character of surface Gauss statistics and self-shadow and is obtained by measurement and modeling in advance. The relative positions of the space-based target, the background radiation sources and the observation platform were determined based on coordinate conversion to judge contributing surface of the target to observation system. Then a mathematical model on visible characteristics of the space target for the given optical system was built by summing reflection components of all the surfaces. Simulation of visible characteristics of the space-based target in orbit was achieved according to its given geometrical dimensions, physical parameters and orbital parameters. The results show that the method is effective for analysis on visible characteristics of the space-based target when single reflection is considered and its surface is regularly described in a surface equation, which provides a way to real-time calculation of visible characteristics of the space-based target.

Development of low‐cost imaging system for laser metal deposition processes

PurposeThe melt pool created by a laser is one of the most important factors affecting the quality of the deposit in a laser metal deposition (LMD) process. The high‐intensity infrared (IR) radiation emitted by the melt pool saturates a conventional camera sensor preventing useful data acquisition. The purpose of this paper is to discuss the development of a low‐cost vision system to monitor the size of the melt pool for in‐process quality control of the deposit.Design/methodology/approachAccording to the black body radiation theory, there is no radiation emitted in the ultraviolet (UV) region from the melt pool created in the LMD process. IR radiation and visible light are the only radiations inherent to the LMD process. UV illumination is utilized along with narrow band pass filters on a USB camera to achieve a clear image of the melt pool while IR radiation of the process is blocked out. The melt pool size and shape were closely monitored during the deposition process.FindingsA clear image of the melt pool was obtained using a relatively low‐cost imaging system during laser deposition process.Originality/valueTraditional approaches to vision systems in high‐intensity processes use a high‐speed video camera fitted with IR filters to prevent saturation of the camera sensor. Such systems are usually complex and expensive to run and maintain. This paper demonstrates an alternative and lower cost method to achieve in process monitoring in an LMD process.

The relation between a black hole and a general black body system

Taking a black hole as a black body system, using general black body radiation theory, a Schwarzschild black hole and a Kerr–Newman black hole are investigated respectively. It is concluded that a black hole can be regarded as an ideal general black body system exactly for the changing process only. However, a stationary global black hole cannot be smoothly regarded as a general black body system. A black hole has some special characteristics which different from a general thermodynamics system. This conclusion means that a black hole should be inherently dynamical, at least when it is taken as a black body system.

Breakdown of the Planck blackbody radiation law at nanoscale gaps

The Planck theory of blackbody radiation imposes a limit on the maximum radiative transfer between two objects at given temperatures. When the two objects are close enough, near-field effects due to tunneling of evanescent waves lead to enhancement of radiative transfer above the Planck limit. When the objects can support electromagnetic surface polaritons, the enhancement can be a few orders-of-magnitude larger than the blackbody limit. In this paper, we summarize our recent measurements of radiative transfer between two parallel silica surfaces and between a silica microsphere and a flat silica surface that show unambiguous evidence of enhancement of radiative transfer due to near-field effects above the Planck limit.

The odd couple: Boltzmann, Planck and the application of statistics to physics (1900-1913)

In the last forty years a vast scholarship has been dedicated to the reconstruction of Planck's theory of black-body radiation and to the historical meaning of quantization. Since the introduction of quanta took place for combinatorial reasons, Planck's understanding of statistics must have played an important role. In the first part of this paper, I sum up the main theses concerning the status of the quantum and compare the arguments supporting them. In the second part, I investigate Planck's usage of statistical methods and the relation to Boltzmann's analogous procedure. I will argue that this way of attacking the problem is able to give us some interesting insights both on the theses stated by the historians and on the general meaning of Planck's theory.

Near-field radiative heat transfer between a sphere and a substrate

Near-field force and energy exchange between two objects due to quantum electrodynamic fluctuations give rise to interesting phenomena such as Casimir and van der Waals forces and thermal radiative transfer exceeding Planck's theory of blackbody radiation. Although significant progress has been made in the past on the precise measurement of Casimir force related to zero-point energy, experimental demonstration of near-field enhancement of radiative heat transfer is difficult. In this work, we present a sensitive technique of measuring near-field radiative transfer between a microsphere and a substrate using a bimaterial atomic force microscope cantilever, resulting in ``heat transfer-distance'' curves. Measurements of radiative transfer between a sphere and a flat substrate show the presence of strong near-field effects resulting in enhancement of heat transfer over the predictions of the Planck blackbody radiation theory.

Quantum Mechanics: Basic Concepts, From Big-Bang To Brain / Kuantum Mekaniği: Temel Kavramlar, Büyük Patlamadan Beyine [Turkish

Quantum mechanics deals with the behaviour of matter and light on the atomic and subatomic scale. It attempts to describe and account for the properties of molecules and atoms and their constituents--electrons, protons, neutrons, and other more esoteric particles such as quarks and gluons. Its concepts frequently conflict with common-sense notions derived from observations of the everyday world. Quantum mechanics has attracted some of the ablest scientists of the 20th century, and they have erected what is perhaps the finest intellectual edifice of the period. Quantum mechanics is concerned with phenomena that are so small-scale that they cannot be described in classical terms. The history of quantum mechanics may be divided into three main periods. The first began with Planck's theory of black-body radiation in 1900; it may be described as the period in which the validity of Planck's constant was demonstrated but its real meaning was not fully understood. The second period began with the quantum theory of atomic structure and spectra proposed by Niels Bohr in 1913. True quantum mechanics appeared in 1926, reaching fruition nearly simultaneously in a variety of forms--namely, the matrix theory of Max Born and Werner Heisenberg, the wave mechanics of Louis V. de Broglie and Erwin Schrodinger, and the transformation theory of P.A.M. Dirac and Pascual Jordan.

Extending the photon mapping method for realistic rendering of hot gaseous fluids

AbstractWith the increased sophistication and use of heated gas, fire, and explosion simulations in computer graphics applications, there is a corresponding impetus to improve the visual realism in the rendering of such simulated phenomena. In visualizing these turbulent fluids, an appropriate incorporation of their incandescent properties into the rendering significantly enhances the realism of visual effects. In this paper, we effectively synthesize the light emission phenomena of hot gaseous fluids by extending the photon mapping global illumination method. In particular, we add two new photon maps to capture the thermal radiation effects. First, we define an emission photon map to store the photons emitted within hot gaseous fluids. Second, we utilize additional flash and flash reflection photon maps, which are effective in creating a visual effect of light that intensively and instantly propagates outside hot gaseous fluids, visually capturing shock waves. Our current technique, while based on the theory of blackbody radiation, is parameterized to enable an animator to generate a wide range of visual effects with fairly intuitive user control. We demonstrate the effectiveness of our new rendering technique and user‐controlled generation of visual effects with several example pictures and animations. Copyright © 2005 John Wiley & Sons, Ltd.

Thermal Equilibrium Between Radiation and Matter

In 1916, Einstein rederived the blackbody radiation law of Planck that originated the idea of quantized energy one hundred years ago. For this purpose, Einstein introduced the concept of transition probability, which had a profound influence on the development of quantum theory. In this article, we adopt Einstein's assumptions with two exceptions and seek the statistical condition for the thermal equilibrium of matter without referring to the inner details of either statistical thermodynamics or quantum theory. It is shown that the conditions of thermodynamic equilibrium of electromagnetic radiation and the energy balance of thermal radiation by the matter, between any of its two energy-states, not only result in Planck's radiation law and the Bohr frequency condition, but they remarkably yield the law of the statistical thermal equilibrium of matter: the Maxwell–Boltzmann distribution. Since the transition probabilities of the modern quantum theory of radiation coincide with their definition in Einstein's theory of blackbody radiation, the presented deduction of the Maxwell–Boltzmann distribution is equally valid within the bounds of modern quantum theory. Consequently, within the framework of the fundamental assumptions, the Maxwell–Boltzmann distribution of energy-states is not only a sufficient, but a necessary condition for thermal equilibrium between the matter and radiation.

Mesoscopic SNS junctions and their application to SQUIDs and millimeter-wave detectors

Mesoscopic SNS junctions have been studied both in the ballistic and diffusive regimes. SNS junctions in the ballistic regime behave as an ideal Fermion oscillator which is to be compared with the Boson oscillator or the Planck theory of blackbody radiation. The current of mesoscopic SNS junctions in the diffusive regime has the same phase dependence as that of dirty-limit short weak links derived by a transport equation. Recent theories of mesoscopic SNS junctions have successfully unified the theories of the tunnel Josephson junction, the clean-limit short weak link and the dirty-limit short weak link which look very different conceptionally. We can even observe transitions among the three types of junctions when we change the transmission coefficients of the barriers between the superconducting electrodes experimentally. We looked experimentally for the optimum transmission coefficient which gives the minimum low-frequency telegraph noise in order to make a low-noise SQUID magnetometor for brain science. We have observed signals of 5 fT from human brains with a good signal-to-noise ratio using the SQUID magnetometor of the SNS junctions. The 64-channel SQUID magnetometer of SNS junctions has confirmed that mesoscopic SNS junctions are important not only theoretically but also practically. These data could encourage people studying SNS junctions of high-Tc superconductors.

Black-body radiation in plasmas

The theory of black-body radiation in thermal equilibrium with a homogeneous and isotropic plasma is presented. The relevant thermodynamic quantities of the radiation are obtained. The presence of the plasma changes qualitatively and often quantitatively the concept of black-body radiation, essentially through the effect of plasma density.

Blackbody radiation from hot two-dimensional electrons in AlxGa1-xAs/GaAs heterojunctions.

We have studied the broad-band far-infrared (FIR) radiation from hot two-dimensional (2D) electrons in selectively doped ${\mathrm{Al}}_{\mathit{x}}$${\mathrm{Ga}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$As/GaAs heterojunctions. The combination of a composite Si bolometer and a magnetic-field-tuned InSb cyclotron resonance filter allows a spectroscopic as well as an intensity analysis of the FIR emission from hot 2D electrons. It is found that the radiation spectra are well explained by the theory of blackbody radiation and the emissivity assuming a classical Drude conductivity. The behavior of the determined effective blackbody temperatures of hot 2D electrons is quantitatively explained by a theory of acoustic- and optical-phonon emissions.

Evidence from the special relativity and blackbody radiation theories for the existence of photons possessing zero kinetic energy

The traditional interpretation of radiative emission and absorption asserts that photons are created and annihilated in such processes. A Gedanken experiment is considered in which kinetic energy from observed photons is systematically removed until a limit of zero is reached. With the help of the relativistic Doppler effect, it is shown that even for infinitesimally small kinetic energies the photons continue to exist, since in other interial systems they will be observed to have a much higher energy/frequency falling in an easily detectable range. An alternative explanation for absorption and emission processes can be formulated on this basis in terms of real photons with exactly zero kinetic energy being present before or after radiative interactions. Bolstering this hypothesis is the fact that the statistical mechanical treatment of photons interacting with oscillators in blackbody radiation theory predicts an infinite density of photons of this energy, both in the original Planck formulation employing Maxwell-Boltzmann statistics and in the subsequent Bose-Einstein description. The Bohr relation, E = hv, also makes clear that it is not possible to observe photons in this E = 0 state because a null frequency (or infinite wavelength) cannot be observed, so no contradiction results on this basis. It is pointed out that the Einstein mass dilation formula indicates that photons with zero kinetic energy can move with speeds less than c, down to and including a value of zero. It can also be shown that ordinary conservation of energy/momentum laws lead to the prediction of quantization phenomena in absorption and radiation processes, because of the much smaller mass of photons vis-à-vis atoms. These considerations demonstrate that the E = 0 state is greatly preferred as the product of absorption because of the requirement to have the interaction occur in a relatively narrow region of space-time. There is thus strong evidence that photons are not created and annihilated in radiative processes but simply have their kinetic energy changed either to or from a zero value. Accordingly, a very high density of zero-energy photons is expected to exist uniformly throughout the universe. Finally, this development suggests that one should subject the creation-annihilation hypothesis to careful scrutiny in other areas of physics as well.

Quantitative measurement of radiation properties for opaque and semi-transparent greybodies

Because of the lack of theory and methods of measuring the ambient radiation in real situations, it is impossible to quantify the self-radiation properties of a target. Our earlier paper, (13) proposed a theory, “Equivalent Blackbody Radiation Theory,” and a design method for infrared systems that can measure quantitatively the ambient radiation and self-radiating properties of opaque targets. We now extend our treatment to the more general case which includes opaque, semi-transparent and transparent objects. As examples, the ambient radiation in different situations, the self-radiation properties of an opaque metal plate and a semi-transparent crystal, and the true temperature difference of human breath during inspiration and exhalation are measured quantitatively and successfully.

Equivalent blackbody radiation theory and its use in the radiation property measurement of a semitransparent body

To quantitatively measure the ambient radiation reflected by a target, in an earlier paper [Zhang et al., Appl. Opt. 25, 3683-3689 (1986)] we presented the equivalent blackbody radiation theory. In this paper we give a theoretical demonstration of that theory and generalize it from the case of an opaque body to the case of a semitransparent body. Several methods are proposed to measure the transmittance, the emissivity, the reflectance, and the true temperature of an opaque or semitransparent body. Good quantitative experimental results are obtained.

The Logical Inconsistency of the Old Quantum Theory of Black Body Radiation

The old quantum theory of black body radiation was manifestly logically inconsistent. It required the energies of electric resonators to be both quantized and continuous. To show that this manifest inconsistency was inessential to the theory's recovery of the Planck distribution law, I extract a subtheory free of this manifest inconsistency but from which Planck's law still follows.

Theoretical Concepts in Physics: An Alternative View of Theoretical Reasoning in Physics for Final‐Year Undergraduates

Acknowledgements Preface 1. Introduction 2. Tycho Brahe, Kepler and Newton - the origin of Newton's law of gravitation 3. The origin of Maxwell's equations 4. How to rewrite the history of electromagnetism 5. Approaches to mechanics and dynamics 6. Simple thermodynamics 7. The kinetic theory of gases and the origin of statistical mechanics 8. Black body radiation up to 1895 9. 1895-1900: Planck and the spectrum of black body radiation 10. Planck's theory of black body radiation 11. Einstein and the quantisation of light 12. The story concluded - a further classical paper by Einstein 13. Special relativity - a study in invariance 14. An introduction to general relativity 15. Cosmology 16. Epilogue References and further reading Index.

Sun and lamps

A nonstandard method for determining solar temperature has been presented. This method is based on the comparison between the brightness of a commercially available incandescent lamp and the Sun. This comparison is quantitative, due to the well-known properties of tungsten. Planck’s law too has a fundamental role in this comparison. A silicon cell with an interference filter which has a central wavelength of 600 nm is used to examine the two sources of light. A quite satisfactory value of the solar temperature—about 5700 K—has been obtained in this way, and some interesting points are raised in connection with the radiation constant c2 of Planck’s law. The experiment may be considered as an advanced project concerning solar energy teaching or blackbody radiation theory.

Was Poincare a herald of quantum theory?

The authors describe the general attitude of Poincare toward quantum theory in his last popular lectures and in the two articles 'Sur la theorie des quanta'. They show that Poincare remained a classical scientist opposed to the new theory. Although he failed in avoiding the quantum hypothesis, Poincare did not renounce the defence of classical physics. The authors argue that Poincare ignored the implications of his own work on the N-body problem for the theory of black-body radiation.

Surface area dependent corrections in the theory of black body radiation

For a certain class of boundary geometries, the solutions of the electromagnetic vector wave equation in a finite lossless closed cavity can be classified into E- and H-type modes. We show that each kind of solution contributes a surface area dependent term to the corresponding asymptotic eigenvalue densities, D E and D H. These surface terms are equal, but have opposite signs. This constitutes a new proof of the well known vanishing of the first order correction of the complete mode density D E + D H = D. We present a formula for the difference of the E- and H-type densities, D E − D H , which is stricly valid in the asymptotic limits of infinite frequency or infinite cavity volume. We show that this formula is in good agreement with computed eigenvalue spectra obtained from the first 10 6 modes for several cavity geometries, i.e. the cube, square prisms, cylinders, sectors of cylinders, the sphere, and sectors of the sphere. Furthermore, we study the surface correction of the time auto-correlation functions of the electric and magnetic field components.