Poster - Stanford University
... Reflection from the accretion disc imprints a number of atomic features on the spectrum we observe, not least emission lines. When atoms are excited, their electrons emit light at very specific energies (colours). It is why different metal compounds glow different colours when heated e.g. sodium str ...
... Reflection from the accretion disc imprints a number of atomic features on the spectrum we observe, not least emission lines. When atoms are excited, their electrons emit light at very specific energies (colours). It is why different metal compounds glow different colours when heated e.g. sodium str ...
ph507lecnote06
... star (its power or luminosity in watts) is just L = 4R2T4 since the surface area of a sphere of radius R is 4R2 To summarise: A blackbody radiator has a number of special characteristics. One, a blackbody emits some energy at all wavelengths. Two, a hotter blackbody emits more energy per unit are ...
... star (its power or luminosity in watts) is just L = 4R2T4 since the surface area of a sphere of radius R is 4R2 To summarise: A blackbody radiator has a number of special characteristics. One, a blackbody emits some energy at all wavelengths. Two, a hotter blackbody emits more energy per unit are ...
Astronomy 120
... 11. The Ring Nebula in Lyrae is a planetary nebula with an angular diameter of 72 seconds of arc at a distance of 5000 ly. a) What is its linear diameter? b) If the Ring Nebula is expanding at a velocity of 15 km/sec, typical of planetary nebulae, how old is it? Assume a uniform rate of expansion. ...
... 11. The Ring Nebula in Lyrae is a planetary nebula with an angular diameter of 72 seconds of arc at a distance of 5000 ly. a) What is its linear diameter? b) If the Ring Nebula is expanding at a velocity of 15 km/sec, typical of planetary nebulae, how old is it? Assume a uniform rate of expansion. ...
Chap 7 - College of Science | Oregon State University
... Fahrenheit based on human body temperature and freezing point of a mixture of water and salt. - Water freezes at 32oF; boils at 212oF. - There are 180 degrees between these two points. Kelvin based on absolute zero. - Also called absolute scale. - Absolute zero is the lowest possible temperature tha ...
... Fahrenheit based on human body temperature and freezing point of a mixture of water and salt. - Water freezes at 32oF; boils at 212oF. - There are 180 degrees between these two points. Kelvin based on absolute zero. - Also called absolute scale. - Absolute zero is the lowest possible temperature tha ...
Lecture 4: Heat transfer
... The Stefan–Boltzmann law, also known as Stefan's law, states that the total energy radiated per unit surface area of a body in unit time is directly proportional to the fourth power of the body's temperature in Kelvin T (also called absolute temperature): ...
... The Stefan–Boltzmann law, also known as Stefan's law, states that the total energy radiated per unit surface area of a body in unit time is directly proportional to the fourth power of the body's temperature in Kelvin T (also called absolute temperature): ...
Homework Assignment # 1
... 3. Two square plates are made out of the same homogeneous material, and both are initially heated to 100◦ . All four sides of the first plate are held at 0◦ , while for the second plate one of its sides is insulated and the other 3 held at 0◦ . Which plate cools down the fastest? How much faster? As ...
... 3. Two square plates are made out of the same homogeneous material, and both are initially heated to 100◦ . All four sides of the first plate are held at 0◦ , while for the second plate one of its sides is insulated and the other 3 held at 0◦ . Which plate cools down the fastest? How much faster? As ...
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.