# Black body radiation Definition and 82 Discussions

Black-body radiation is the thermal electromagnetic radiation within or surrounding a body in thermodynamic equilibrium with its environment, emitted by a black body (an idealized opaque, non-reflective body). It has a specific spectrum of wavelengths, inversely related to intensity that depend only on the body's temperature, which is assumed for the sake of calculations and theory to be uniform and constant.The thermal radiation spontaneously emitted by many ordinary objects can be approximated as black-body radiation. A perfectly insulated enclosure that is in thermal equilibrium internally contains black-body radiation and will emit it through a hole made in its wall, provided the hole is small enough to have a negligible effect upon the equilibrium.
In a dark room, a black body at room temperature appears black because most of the energy it radiates is in the infrared spectrum and cannot be perceived by the human eye. Since the human eye cannot perceive light waves below the visible frequency, a black body at the lowest just faintly visible temperature subjectively appears grey, even though its objective physical spectrum peak is in the infrared range. The human eye essentially does not perceive color at low light levels. When the object becomes a little hotter, it appears dull red. As its temperature increases further it becomes bright red, orange, yellow, white, and ultimately blue-white.
Although planets and stars are neither in thermal equilibrium with their surroundings nor perfect black bodies, black-body radiation is used as a first approximation for the energy they emit. Black holes are near-perfect black bodies, in the sense that they absorb all the radiation that falls on them. It has been proposed that they emit black-body radiation (called Hawking radiation), with a temperature that depends on the mass of the black hole.The term black body was introduced by Gustav Kirchhoff in 1860. Black-body radiation is also called thermal radiation, cavity radiation, complete radiation or temperature radiation.

View More On Wikipedia.org
1. ### Why optical pyrometer gives a low reading?

From my knowledge, the optical pyrometer determines temperature of a body based on the visible part of the heat radiation spectrum emitted by a body. Now the iron piece was red hot inside the furnace as well as outside the furnace, so it is emitting heat radiation in the visible part both while...
2. ### Application Of Kirchoff Law (Desert)

Homework Statement:: Sand is rough and black so it is a good absorber and radiator of heat depending on temperature. During the day, sand's radiation of the sun's energy superheats the air and causes temperatures to soar. But, at night most of the heat in the sand quickly radiates into the air...
3. ### I Continuous Spectrum and Energy levels of Electrons (Energy Bands)

My book says that emission spectra are produced when an electron in excited state jump from excited to lower energy states. It also states that solids and liquids produce continuous spectra and it depends upon temperature only (is this black body radiation?). I know, Electrons around a nucleus...
4. ### I Visualising an alternative formulation of Planck's Radiation Law

I've come across this alternative formulation of Planck's Law which links the number density to energy gap n(E) = \frac{2\pi}{c^2 h^3} \frac{E^2}{exp\big(\frac{E-\mu}{k_BT})-1} I've tried visualising this relation and I imagine it will look similar to the spectral density relation but I'm just...
5. ### A Equipartition of energy in the modes of a resonant cavity

I think the answer for this may be straightforward, but I don't see anywhere that explains this from the scratch: A large resonant cavity with a small hole is used to approximate an ideal black body. I understand the conditions for the modes inside the cavity. But there are two points that...

I am quite confused, as I start this question. I can easily find the following when searching up Planck's law: However, this is not u. My prof is quite unclear and sometimes chooses his own variables as he sees fit, so i am not sure if this would be equivalent to what he is looking for u(λ)dλ...
7. ### I Radiance and energy density of a black body

How can I find the relation between the radiance and the energy density of a black body? According to Planck's law, the energy density inside a blackbody cavity for modes with frequency ##\nu \in [\nu, \nu + \mathrm{d}\nu]## is given by  \rho(\nu, T)\mathrm{d}\nu =...
8. ### How a solid body emits a lower frequency photon than absorbed

I’m trying to understand how a solid body changes the wavelength of radiation it re-radiates from that which it originally absorbed. I’m thinking in context to the way that the Earth absorbs higher frequency radiation from the sun, but when it re-emits the energy it’s at a much lower frequency...
9. ### Infrared thermometry remote sensing

hi all, This isn't simply physics but is very much related. I'm trying to make an infrared thermometer or some means of remote temperature measurements for temperatures from 0 degree C to around 400 degree C I started with looking up low cost silicon photo diodes / photo transistors e.g. on...
10. ### How to calculate color temperature?

I am looking for calculating color temperature in the IR/Microwave scale frequencies, for room temperature, 273K, 263K, 253K, all google is showing is about visible light and about display systems.
11. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 1: Black Body Radiation I

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
12. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 2: Black Body Radiation II

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
13. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 3: Black Body Radiation III

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
14. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 6: Black Body Radiation VI

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
15. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 7: Black Body Radiation VII

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
16. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 8: Radiation as a collection of particles called photons

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
17. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 9: Quantum Hypothesis and specific heat of solids

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
18. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 10: Bohr's Model of hydrogen spectrum

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
19. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 11: Wilson Sommerfeld quantum condition I

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
20. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 12: Wilson Sommerfeld quantum condition II

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
21. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 13: Wilson Sommerfeld quantum condition III

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
22. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 14: Quantum conditions and atomic structure

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
23. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 15: Eienstien's A and B coefficients

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
24. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 16: Stimulated emission and amplification of light in a LASER

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
25. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 17: Brief description of a LASER

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
26. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 18: Introduction to the correspondence principle

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
27. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 19: General nature of the correspondence principle

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
28. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 20: Selection rules (for transitions) through the correspondence principle

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
29. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 21: Applications of the correspondence principle

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
30. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 22: Heisenberg's formulations of quantum mechanics I

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
31. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 23: Heisenberg's formulations of quantum mechanics II

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
32. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 24: Heisenberg's formulations of quantum mechanics III

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
33. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 25: Brief introduction to matrix mechanics

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
34. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 26: Introduction to waves and wave equation

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
35. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 27: Sationary waves eigen values and eigen functions

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
36. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 28: Matter waves and their experimental detection

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
37. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 29: Representing a moving particle by a wave packet

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
38. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 30: Stationary-state Schrodinger equation

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
39. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 31: Solution of the stationary-state Schrodinger equation for a SHO

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
40. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 32: Equivalance of Heisenberg and the Schrodinger formulations I

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
41. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 33: Equivalance of Heisenberg and Schrodinger formulations II

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
42. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 34: Born interpretation of the wavefunction

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
43. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 35: Uncertainty principle and its simple applications

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
44. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 36: Time dependent Schrodinger equation

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
45. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 37: Ehrenfest theorem

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
46. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 38: Solution of Schrodinger equation for a particle in delta functions

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
47. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 39: Solution of Schrodinger equation for a particle in a finite well

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
48. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 40: Solution of a one dimensional Schrodinger equation for bound states I

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
49. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 41: Solution of a one dimensional Schrodinger equation for bound states II

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/
50. ### Introductory Quantum Mechanics with Prof. Manoj Harbola (NPTEL):- Lecture 42: Reflection and transmission of particles across a potential barrier

All copyright reserved to Prof. Harbola and NPTEL, Govt. of India. Duplication punishable offence. Course Website: http://www.nptel.ac.in/courses/115104096/