What is Hawking radiation?
what is blackbody spectrum?
what is blackbody spectrum?
Hawking radiation, also known asHawking–Zel'dovich radiation,isblackbody radiationthat is predicted to be released byblack holes, due toquantumeffects near theevent horizon. It is named after the physicistStephen Hawking, who provided a theoretical argument for its existence in 1974,and sometimes also afterJacob Bekenstein, who predicted that black holes should have a finiteentropy. Black-body radiation has a characteristic, continuousfrequency spectrumthat depends only on the body's temperature,[8]called the Planck spectrum orPlanck's law. The spectrum is peaked at a characteristic frequency that shifts to higher frequencies with increasing temperature, and atroom temperaturemost of the emission is in theinfraredregion of theelectromagnetic spectrum.[9][10][11]As the temperature increases past about 500 degreesCelsius, black bodies start to emit significant amounts of visible light. Viewed in the dark by the human eye, the first faint glow appears as a "ghostly" grey (the visible light is actually red, but low intensity light activates only the eye's grey-level sensors). With rising temperature, the glow becomes visible even when there is some background surrounding light: first as a dull red, then yellow, and eventually a "dazzling bluish-white" as the temperature rises.[12][13]When the body appears white, it is emitting a substantial fraction of its energy asultraviolet radiation. The Sun, with aneffective temperatureof approximately 5800 K,[14]is an approximate black body with an emission spectrum peaked in the central, yellow-green part of thevisible spectrum, but with significant power in the ultraviolet as well.
Black-body radiation provides insight into thethermodynamic equilibriumstate of cavity radiation. If eachFourier modeof the equilibrium radiation in an otherwise empty cavity with perfectly reflective walls is considered as a degree of freedom capable of exchanging energy, then, according to theequipartition theoremof classical physics, there would be an equal amount of energy in each mode. Since there are an infinite number of modes this implies infiniteheat capacity(infinite energy at any non-zero temperature), as well as an unphysical spectrum of emitted radiation that grows without bound with increasing frequency, a problem known as theultraviolet catastrophe. Instead, in quantum theory theoccupation numbersof the modes are quantized, cutting off the spectrum at high frequency in agreement with experimental observation and resolving the catastrophe. The study of the laws of black bodies and the failure of classical physics to describe them helped establish the foundations ofquantum mechanics.
Black-body radiation has a characteristic, continuousfrequency spectrumthat depends only on the body's temperature,[8]called the Planck spectrum orPlanck's law. The spectrum is peaked at a characteristic frequency that shifts to higher frequencies with increasing temperature, and atroom temperaturemost of the emission is in theinfraredregion of theelectromagnetic spectrum.[9][10][11]As the temperature increases past about 500 degreesCelsius, black bodies start to emit significant amounts of visible light. Viewed in the dark by the human eye, the first faint glow appears as a "ghostly" grey (the visible light is actually red, but low intensity light activates only the eye's grey-level sensors). With rising temperature, the glow becomes visible even when there is some background surrounding light: first as a dull red, then yellow, and eventually a "dazzling bluish-white" as the temperature rises.[12][13]When the body appears white, it is emitting a substantial fraction of its energy asultraviolet radiation. The Sun, with aneffective temperatureof approximately 5800 K,[14]is an approximate black body with an emission spectrum peaked in the central, yellow-green part of thevisible spectrum, but with significant power in the ultraviolet as well.
Black-body radiation provides insight into thethermodynamic equilibriumstate of cavity radiation. If eachFourier modeof the equilibrium radiation in an otherwise empty cavity with perfectly reflective walls is considered as a degree of freedom capable of exchanging energy, then, according to theequipartition theoremof classical physics, there would be an equal amount of energy in each mode. Since there are an infinite number of modes this implies infiniteheat capacity(infinite energy at any non-zero temperature), as well as an unphysical spectrum of emitted radiation that grows without bound with increasing frequency, a problem known as theultraviolet catastrophe. Instead, in quantum theory theoccupation numbersof the modes are quantized, cutting off the spectrum at high frequency in agreement with experimental observation and resolving the catastrophe. The study of the laws of black bodies and the failure of classical physics to describe them helped establish the foundations ofquantum mechanics.
