150, I4hen a nuclear veapon is eXplOded above ground, the first noticeabl-e effect is a blinding flash of intense white light, stTong enough to tenporarily blind or at least dazzle observers out ta many kilonetres distant fTo!0 the explosion. fhe general impression is that the whole sky is brilliantly illuminated' The light is enitted from the surface of the trfirebaI1", a roughly spherical mass of ""IV rr"i .i,. (trr" temperature is of the order of l-0 nillion degrees centigrade) rnd- *.u.po. residues, which develops qui ckly around the exploding weapon and continues to grov until it reaches a maximum radius which depends on the yieId. For a weapon with a yield of 10 to 20 kt., i'e. that of the Hiroshina and Nagasaki bombs, ttre maximr:m radius is approxinately 200 n' and its developmentA/ 35 /392a.ncLi sb .Annex rai,,..e )) takes about one second. During that time, and for some tine after, the fireball,emits the"'nal radiation both as light and - mainly - heat. Fina11y, the thernalradiation dies avay as the fireball is coofed and transforned into ihe mushroom_shaped. expl-osion el,oud. By then, about one third of the explosiwe energy hasbeen released as heat,
**Analysis**
The text appears to be a technical description of the effects of a nuclear explosion, focusing on the physics of the blast, the radiation emitted, and the subsequent development of the explosion. The language used is formal and scientific, suggesting a technical or academic context. The topic is not related to human activities or societal issues, but rather a natural phenomenon.

**Category**
Science and technology