LD (50) (30) is the radiation required to

Ans) a (Kill 50% of the ...30days) Ref park 20th edThe median lethal dose, LD50 (abbreviation for "Lethal Dose, 50%"), LC50 (Lethal Concentration, 50%) or LCt.50 (Lethal Concentration & Time) of a toxic substance or radiation is the dose required to kill half the members of a tested population. LD50 figures are frequently used as a general indicator of a substance's acute toxicity.The related quantities LD50/30 or an LD50/60 are used to refer to a dose that without treatment will be lethal to 50% of the population wiihin (respectively) 30 or 60 days. These measures are used more commonly withinRadiation Health Physics, as survival beyond 60 days usually results in recovery.