Thermal radiation principle: The statement “all bodies above absolute zero emit electromagnetic radiation at various wavelengths” is known as

Introduction / Context:
Thermal remote sensing and heat transfer rely on fundamental radiation laws. A core idea is that any body with temperature above 0 K continuously emits electromagnetic radiation. Recognizing which named law encapsulates this principle helps anchor later formulas for spectral distribution and total emission.

Given Data / Assumptions:

• Objects have temperatures T > 0 K.
• Emission spans a range of wavelengths with a temperature-dependent distribution.
• We refer to classical radiation laws used in physics and remote sensing.

Concept / Approach:
Planck's law provides the spectral radiance distribution of a blackbody as a function of wavelength (or frequency) and temperature. Embedded in this is the principle that any body above absolute zero emits radiation, with intensity and peak wavelength governed by temperature (Wien's law) and total power given by Stefan–Boltzmann law. Lambert's cosine law concerns angular distribution of ideal diffuse emitters/reflectors, not the existence of emission itself.

Step-by-Step Solution:
Associate the statement with spectral emission: continuous thermal radiation exists for T > 0 K.Recall that Planck's formulation quantifies spectral radiance and thus implies emission at all wavelengths with temperature dependence.Differentiate from Lambert's cosine law (directional cosine) and from fabricated terms (e.g., “Plancktan”).Select Planck's law as the correct named law.

Verification / Alternative check:
Planck's law reduces to Wien's displacement law (for peak) and integrates to Stefan–Boltzmann law (for total), reinforcing that it is the foundational spectral statement of thermal emission.

Why Other Options Are Wrong:
Plancktan's law: Not a real physical law.Lambert's cosine law: Describes angular intensity of diffuse surfaces, not existence/spectrum of emission.None of these: Incorrect because Planck's law applies.Stefan–Boltzmann: Gives total emitted power ∝ T^4, not the general spectrum/existence statement.

Common Pitfalls:
Confusing the total-power law (Stefan–Boltzmann) with the spectral distribution (Planck) or with angular distribution laws (Lambert).

Final Answer:
Planck's law.