What are the components of incident radiation, or radiation striking a surface?

• A. E+R+T=1.0
• B. I+R+T=1.0
• C. A+R+T=1.0
• D. Q+R+T=1.0

Answer: (C)

When infrared radiation meets a surface, it is divided into three parts: what is absorbed by the material, what is reflected away, and what is transmitted through the material. These fractions add up to the total incident energy. If we normalize the incident energy to 1.0, the balance is Absorbed + Reflected + Transmitted = 1.0. This expression correctly represents how incident radiation behaves at a surface. Other letters like E, I, or Q aren’t standard names for these components, so they don’t describe the energy balance. And in opaque materials, transmission is zero, so Absorbed plus Reflected would still equal 1.0.