Past exam of the short options paper shared by Prelims and Parts A and B of the physics course of the University of Oxford / 2017 / S16 / 1 / 5 / Solution

The inferred parameters give ${\lambda }_D\simeq 6.46\times 10^{-11}$ m and $\boxed{N_D\simeq 0.28}$, or $n_e{\lambda }_D^3\simeq 0.067$ without the spherical factor. Neither is much larger than one. Thus a good classical weakly coupled plasma approximation is not justified. Correlations, collisions and potentially degeneracy matter at this density; treating the preceding 18.7 eV as a reliable temperature measurement would overstate what this simple model establishes.