Which term is the reflectivity property of a surface often expressed as a ratio or percentage?

Which term is the reflectivity property of a surface often expressed as a ratio or percentage?

• A. Albedo
• B. Transmittance
• C. Absorptivity
• D. Emittance

Answer: (A)

Albedo describes how much of the incoming radiation is reflected by a surface. It is defined as the ratio of reflected radiant flux to incident radiant flux, so it’s a dimensionless quantity that’s often expressed as a decimal or a percent. This makes albedo a measure of reflectivity: bright surfaces like fresh snow have high albedo because they reflect most of the incoming light, while dark surfaces like asphalt have low albedo because they absorb more. The other terms describe different paths for the incoming energy. Transmittance is the fraction that passes through a material, absorptivity is the fraction that is absorbed, and emittance is the energy a surface emits due to its temperature. For opaque surfaces, reflectivity (albedo) and absorptivity together account for nearly all the incident energy, since little or no light is transmitted.

Albedo describes how much of the incoming radiation is reflected by a surface. It is defined as the ratio of reflected radiant flux to incident radiant flux, so it’s a dimensionless quantity that’s often expressed as a decimal or a percent. This makes albedo a measure of reflectivity: bright surfaces like fresh snow have high albedo because they reflect most of the incoming light, while dark surfaces like asphalt have low albedo because they absorb more.

The other terms describe different paths for the incoming energy. Transmittance is the fraction that passes through a material, absorptivity is the fraction that is absorbed, and emittance is the energy a surface emits due to its temperature. For opaque surfaces, reflectivity (albedo) and absorptivity together account for nearly all the incident energy, since little or no light is transmitted.