What is the concept of black body?
Blackbody, also spelled black body, in physics, a surface that absorbs all radiant energy falling on it. The term arises because incident visible light will be absorbed rather than reflected, and therefore the surface will appear black.
What is the absorptive power of a black body?
For a perfect black body, Absorptive power is maximum and unity. It has no units and dimensions. a < 1 (for any body) and a = 1 (for perfectly black body).
What is the emissive power of a body?
or Emissive power is the power of a body at a given temperature emitted as radiant thermal energy from a unit surface area of a hot body per unit time. It is also known as spectral emissive power. Basically, it is the total amount of thermal energy emitted per unit area per unit time.
What is emissive power formula?
Complete answer: The total amount of heat energy emitted per unit area per unit time is called emissive power at that temperature. The energy is emitted as radiation in different wavelengths. It is given by- Eg=QAt.
What is difference between emissive power and emissivity?
Emissive power of a material is the rate of radiation emitted through a unit area of the material. Emissivity of a material is defined as the ratio of the rate of radiation emitted through a unit area of the material to that of a blackbody.
What is the relation between reflectivity absorptivity and transmissivity?
Absorptivity (α) is a measure of how much of the radiation is absorbed by the body. Reflectivity (ρ) is a measure of how much is reflected, and transmissivity (τ) is a measure of how much passes through the object.
What is the relation between the rate of convection heat transfer and the rate of mixing in turbulent fluid flow?
The intense mixing of the fluid in turbulent flow enhances heat and momentum transfer between fluid particles, which in turn increases the friction force and the convection heat transfer coefficient.
What is GREY surface?
A gray surface, or graybody, is a surface that reflects/absorbs a given fraction of the thermal radiation a blackbody surface would absorb. More importantly, the graybody/blackbody fraction is independent of radiation wavelength.
What is a gray surface heat transfer?
Gray Body Radiation Heat Transfer Bodies that emit less thermal radiation than a blackbody have surface emissivities e less than 1. If the surface emissivity is independent of wavelength, then the body is called a “gray” body, in that no particular wavelength (or color) is favored.
What is gray surface approximation *?
Explain how the average emissivity of a grey surface can be determined? A grey body is defined as a body with constant emissivity over all wavelengths and temperatures. Such an ideal body does not exist in practice but the assumption is a good approximation for.
What temperature does black body emit radiant energy?
What should be the temperature of black body to emit radiant energy which is independent of the conditions in the surroundings? temperature of black body should be less than zero. temperature of black body should be more than zero. temperature of black body should be equal to zero.
What is the wavelength at which human body radiates maximum energy?
12 microns