Law of reflection:
States that the direction of incoming light (the incident ray), and the direction of outgoing light reflected (the reflected ray) make the same angle with respect to the surface normal, thus the angle of incidence equals the angle of reflection; this is commonly stated as θi = θr.

Thermal Reflectance and Emissivity:

The geometrical micro fiber structure and high diffuse reflection of ORCA Grow Film® lends itself to be a natural insulator and exhibit a low emissivity. ORCA Grow Film® remains highly reflective at wavelengths out past 700nm.

The emissivity of a material (usually written ε or e) is the relative power of its surface to emit heat by radiation. It is the ratio of energy radiated by a particular material to energy radiated by a black body at the same temperature. It is a measure of a material's ability to radiate absorbed energy. Emissivity is a dimensionless quantity, so it does not have units.

In general, the duller and blacker a material is, the closer its emissivity is to 1. The more reflective a material is, the lower its emissivity. Emissivity depends on factors such as temperature, emission angle, and wavelength.

Although it is common to discuss the "emissivity of a material", the emissivity of a material does in general depend on its thickness. The emissivity quoted for materials are for samples of infinite thickness (which, in practice, means samples which are optically thick) — thinner samples of material will have reduced emissivity.

When dealing with non-black surfaces, the deviations from ideal black body behavior are determined by both the geometrical structure and the chemical composition, and follow Kirchhoff's law of thermal radiation: emissivity equals absorptivity (for an object in thermal equilibrium), so that an object that does not absorb all incident light will also emit less radiation than an ideal black body.