lecture11
... Hotter B.B. emitters “emit” more total radiation per unit area. However, a big cold object can emit the same or more energy (depending on how big it is) than a small, hotter one ...
... Hotter B.B. emitters “emit” more total radiation per unit area. However, a big cold object can emit the same or more energy (depending on how big it is) than a small, hotter one ...
A-105 Homework 1
... 8. (2 pts.) Pulsars radiate their energy into space as their magnetic fields interact with the accreting matter. Where does this energy ultimately come from? What happens to the pulsar as it loses its energy? ...
... 8. (2 pts.) Pulsars radiate their energy into space as their magnetic fields interact with the accreting matter. Where does this energy ultimately come from? What happens to the pulsar as it loses its energy? ...
Keeping Warm in Winter - University of Mount Union
... fuzzy down feathers that trap air and prevent convection from carrying away much of their body heat. As a result, their outer feathers are much cooler than their skin, so the loss by radiation is also diminished. Some birds and hibernating mammals can drop their body temperatures which makes the dif ...
... fuzzy down feathers that trap air and prevent convection from carrying away much of their body heat. As a result, their outer feathers are much cooler than their skin, so the loss by radiation is also diminished. Some birds and hibernating mammals can drop their body temperatures which makes the dif ...
1. What is the black hole?
... 5.Could the Sun become a black hole? No, the Sun is much too small to ever become a black hole. A star has to be much more massive than the Sun before it can collapse into a black hole. ...
... 5.Could the Sun become a black hole? No, the Sun is much too small to ever become a black hole. A star has to be much more massive than the Sun before it can collapse into a black hole. ...
electromagnetic spectrum
... Radio waves, microwaves, x-rays, gamma rays, and the spectrum of visible colors are all really the same thing - electromagnetic energy. The differences are their wavelengths. Radio waves are long, measuring as much as hundreds of meters between peaks. Gamma ray wavelengths are extremely short, as li ...
... Radio waves, microwaves, x-rays, gamma rays, and the spectrum of visible colors are all really the same thing - electromagnetic energy. The differences are their wavelengths. Radio waves are long, measuring as much as hundreds of meters between peaks. Gamma ray wavelengths are extremely short, as li ...
Blackbody Radiation
... Blackbody = something that absorbs all electromagnetic radiation incident on it. A blackbodyy does not necessarilyy look black. Its color depends on its temperature. The Sun and other stars behave approximately like blackbodies. The amount of electromagnetic radiation, with a given wavelength, emitt ...
... Blackbody = something that absorbs all electromagnetic radiation incident on it. A blackbodyy does not necessarilyy look black. Its color depends on its temperature. The Sun and other stars behave approximately like blackbodies. The amount of electromagnetic radiation, with a given wavelength, emitt ...
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... 9. You decide to pull out your handy eyepiece, which as a 10mm focal length. Since no one is around to stop you, you decide to look at the stars through each of these expensive telesc ...
... 9. You decide to pull out your handy eyepiece, which as a 10mm focal length. Since no one is around to stop you, you decide to look at the stars through each of these expensive telesc ...
Black body
A black body (also blackbody) is an idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence. A white body is one with a ""rough surface [that] reflects all incident rays completely and uniformly in all directions.""A black body in thermal equilibrium (that is, at a constant temperature) emits electromagnetic radiation called black-body radiation. The radiation is emitted according to Planck's law, meaning that it has a spectrum that is determined by the temperature alone (see figure at right), not by the body's shape or composition.A black body in thermal equilibrium has two notable properties:It is an ideal emitter: at every frequency, it emits as much energy as – or more energy than – any other body at the same temperature.It is a diffuse emitter: the energy is radiated isotropically, independent of direction.An approximate realization of a black surface is a hole in the wall of a large enclosure (see below). Any light entering the hole is reflected indefinitely or absorbed inside and is unlikely to re-emerge, making the hole a nearly perfect absorber. The radiation confined in such an enclosure may or may not be in thermal equilibrium, depending upon the nature of the walls and the other contents of the enclosure.Real materials emit energy at a fraction—called the emissivity—of black-body energy levels. By definition, a black body in thermal equilibrium has an emissivity of ε = 1.0. A source with lower emissivity independent of frequency often is referred to as a gray body.Construction of black bodies with emissivity as close to one as possible remains a topic of current interest.In astronomy, the radiation from stars and planets is sometimes characterized in terms of an effective temperature, the temperature of a black body that would emit the same total flux of electromagnetic energy.