10. Thermal radiation Flashcards
What is thermal radiation?
conduction of heat by using electromagnetic radiation
What is radiance emittance?
how much power is radiated by unit area into a solid angle of 2pi
What does radiance emittance depend on? (2)
- depends on temperature of body
- surface roughness
What is the absorption coefficient of thermal radiation?
ratio of intensity absorbed by the surface and intensity received by the surface
What does absorption coefficient depend on? (2)
- Wavelength
- Temperature
What is Kirchoff’s law?
bodies that emit more absorb more, and ratio of M/alpha is constant
What is the Stefan-boltzmann law?
Total radiant heat energy emitted from a surface is proportional to the fourth power of its absolute temperature
What is Wien’s displacement law?
black boy radiation curve for different temperature peaks at a wavelength that is inversely proportional to the temperature
What is Max Planck’s radiation law?
the radiation energy of a black body is emitted in discrete integer multiples of the quantum : E = hf
What does black body radiation have to do with how we see the sun?
Sun : 5800K so lots of UV radiation and some yellow and red
What is an incandescent lamp?
wire filaments heated until they glow
What is a medical application of thermal radiation?
telethermography : measure the radiant emmittence of thermal radiation of the human body
