The absorptivity of a surface depends upon(i) Direction of reflected r...
It depend upon the direction of incident radiation. Absorptivity is the fraction of total energy absorbed by the body.
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The absorptivity of a surface depends upon(i) Direction of reflected r...
The correct statements regarding the dependence of absorptivity of a surface are:
(i) Direction of reflected radiation
(ii) Temperature of the surface
(iii) Composition
Let's discuss each statement in detail:
(i) Direction of reflected radiation:
The direction of reflected radiation plays a role in determining the absorptivity of a surface. Absorptivity is the ability of a surface to absorb radiation that falls on it. When radiation strikes a surface, it can be absorbed, reflected, or transmitted. The absorptivity of a surface depends on the angle at which the radiation strikes the surface. Surfaces that are rough or irregular tend to have higher absorptivity than smooth surfaces. This is because rough surfaces scatter the incident radiation in many different directions, increasing the chances of absorption.
(ii) Temperature of the surface:
The temperature of a surface also affects its absorptivity. As the temperature of a surface increases, its ability to absorb radiation also increases. This is because at higher temperatures, the atoms or molecules on the surface have more energy, and they are more likely to absorb the incoming radiation. Additionally, the wavelength of radiation absorbed by a surface depends on its temperature. Surfaces at higher temperatures tend to absorb shorter wavelength radiation, such as ultraviolet and visible light, whereas cooler surfaces absorb longer wavelength radiation, such as infrared.
(iii) Composition:
The composition of a surface is another factor that affects its absorptivity. Different materials have different absorptivities for different wavelengths of radiation. For example, metals such as aluminum and silver have low absorptivity in the visible spectrum, leading to their characteristic shiny appearance. On the other hand, materials like black carbon or soot have high absorptivity in the visible spectrum, making them appear black. The absorptivity of a surface depends on the electronic structure and optical properties of the material, as well as its surface roughness.
In conclusion, the correct statements regarding the dependence of absorptivity of a surface are the direction of reflected radiation, the temperature of the surface, and the composition of the surface. These factors collectively determine the ability of a surface to absorb incident radiation.