Shocksizes (top panels) and timescales (bottom panels) as functions of the UV radiation field and different visual extinction A_V computed for shocks propagating at 10 km s⁻¹ in media of densities of 10² (empty squares), 10³ (empty circles), 10⁴ (filled squares), and 10⁵ (filled circles) cm⁻³. The non-varying parameters are set to their standard values (see Table 1). J-type shocks propagating in dense and weakly irradiated clouds are deliberately removed from the figure (see main text), hence the missing points on the left side of each panel.