Which characteristic is important in determining the effect of thermal radiation from a nuclear explosion?

Distance from the explosion is critical in determining the effect of thermal radiation from a nuclear explosion. The intensity of thermal radiation decreases with distance due to the spreading of energy over larger areas. The inverse square law becomes relevant here, meaning that as you move further away from the explosion, the energy received per unit area diminishes significantly. As a result, individuals or objects located closer to the explosion will experience more intense thermal effects, such as burns or ignition of materials, while those further away are less affected.

While other factors like the size of the fireball, weather conditions, and type of terrain could influence specific impacts or effects, the most fundamental aspect influencing the immediate thermal radiation impact remains the distance from the explosion. This distance is the primary determinant in assessing the level of harm inflicted by the intense heat generated during the initial moments of a nuclear detonation.