Continuous opacity due to H at λ 850 nm (solid line, cloud of blue dots), and due to H at λ 1600 nm (dashed line, cloud of red dots), as a function of temperature in the 3D model (dots) and in the ⟨ 3D ⟩ model (lines), respectively. The opacities have been computed according to Eqs. (8.12) and (8.13) by Gray (2005); they are given in units of cm² per neutral hydrogen atom, and have been normalized to 1 at T = 6000 K. Both opacities are proportional to the electron pressure, and their ratio is a simple monotonic function of temperature. Note that κ(H is almost temperature insensitive between T = 4000 and 5000 K.