$P=\sigma A{T}^4$ Multiplies by $A$ because each part of the surface is emitting a certain type of light. Emissivity: $P=e\sigma A{T}^4$ Wein’s displacement law gives the peak wavelength as a function of temperature: $\lambda =\frac{0.0029}{T}$

Inverse square law

Farther an object, the less intensity you get. $I=\frac{P}{4\pi r^2}$