The emissivity is 0...
The concept involved here is Emissivity - the ability to emit energy. e is the usual symbol, and a perfect emitter would have an e of 1. Your perfect black body will have this emissivity of 1.A highly polished surface (polished at all the wavelengths concerned) will have an emissivity much smaller. Polished silver has an emissivity of about 0.02.In general the emissivity of a surface is inversely related to its reflectance, but this does vary with the surface finish, colour, and the mass of the object.It is worth noting, that low emissivity glass is used with effect in the double glazing of windows.
Yes
Dull silver surfaces and shiny white surfaces can have different emissivity values, which means they might not emit the same amount of thermal radiation. Emissivity is a property that quantifies how effectively an object emits thermal radiation compared to a perfect blackbody at the same temperature. A blackbody has an emissivity of 1, and objects with emissivity closer to 1 are better emitters of thermal radiation. Dull surfaces, including dull silver surfaces, typically have higher emissivity compared to shiny surfaces. Shiny surfaces often have lower emissivity because their smooth and reflective nature reduces their ability to emit thermal radiation effectively. White surfaces can vary in terms of their shininess and emissivity. A shiny white surface might have a lower emissivity, while a more matte or dull white surface may have a higher emissivity. Therefore, if the dull silver surface has a higher emissivity compared to the shiny white surface, it will emit more thermal radiation than the shiny white surface at the same temperature. However, it's important to note that the exact emissivity values can vary based on the specific properties and conditions of the surfaces, so it's best to refer to specific emissivity measurements for accurate comparisons.
Yes, in principle, but only if their emissivity is independent of temperature. Generally, emissivity is a very weak function of temperature.
low emissivity
the emissivity of Si is 0.6
The emissivity is 0...
The concept involved here is Emissivity - the ability to emit energy. e is the usual symbol, and a perfect emitter would have an e of 1. Your perfect black body will have this emissivity of 1.A highly polished surface (polished at all the wavelengths concerned) will have an emissivity much smaller. Polished silver has an emissivity of about 0.02.In general the emissivity of a surface is inversely related to its reflectance, but this does vary with the surface finish, colour, and the mass of the object.It is worth noting, that low emissivity glass is used with effect in the double glazing of windows.
Yes
Normal is equal to vertical.Flat object radiates light and heat to hemisphere space.Sometimes,it is convenient to measure the vertical direction.Hemisphere spectral emissivity ε and normal spectral emissivity rate εn have a relationship: ε =Mεn, M is correction factor.
Emissivity of a surface is defined as its effectiveness in emitting thermal radiation. The term photo emissivity is likely used to narrow the focus to emitting visible light.
Dull silver surfaces and shiny white surfaces can have different emissivity values, which means they might not emit the same amount of thermal radiation. Emissivity is a property that quantifies how effectively an object emits thermal radiation compared to a perfect blackbody at the same temperature. A blackbody has an emissivity of 1, and objects with emissivity closer to 1 are better emitters of thermal radiation. Dull surfaces, including dull silver surfaces, typically have higher emissivity compared to shiny surfaces. Shiny surfaces often have lower emissivity because their smooth and reflective nature reduces their ability to emit thermal radiation effectively. White surfaces can vary in terms of their shininess and emissivity. A shiny white surface might have a lower emissivity, while a more matte or dull white surface may have a higher emissivity. Therefore, if the dull silver surface has a higher emissivity compared to the shiny white surface, it will emit more thermal radiation than the shiny white surface at the same temperature. However, it's important to note that the exact emissivity values can vary based on the specific properties and conditions of the surfaces, so it's best to refer to specific emissivity measurements for accurate comparisons.
Yes, in principle, but only if their emissivity is independent of temperature. Generally, emissivity is a very weak function of temperature.
0.79
Lesser emissivity
Zero emissivity means generally no radiation for the far-field. However, for the near-field case, energy may flow to another bodies.