Question

A number of K-40 atoms explode in the human body every second. The number is
A. 3800
B. 38,000
C. 380,000
D. 3,800,000

Answer 1

Human bodies are naturally radioactive, it is because we breath, eat and drink, and various metabolism occurs in our body, because of this our body absorbs the radioactive substances into tissues, organs, and other organ systems, and constantly replenish them ingestion and inhalation.

Complete answer: Human bodies have several naturally occurring radionuclides that are present within our body, and that major one that produces penetrating gamma radiation, which further escapes from the body, is produced from a radioactive isotope of potassium, which is called as K-40.
The human body contains 0.35% of potassium by weight, and K-40 is the primary source of radiation in the body that is mainly because of two reasons, where the first one is we daily ingest potassium through many foods that we eat, potassium is ingested and this potassium is a critically very important element for the functioning of the human body, and it is fairly present in high concentration.
The second one is K-40 emits gamma radiation in little over 10% of its decay, and most of the gamma radiations are an escape from the body is emitted in about one out of 10 disintegrations of K-40, which implies 500 gamma rays are produced for every second. And the amount of K-40 atoms that are exploding in the body are about 38000.
So the correct option is B.

Note: Other than K-40 other radionuclides are present in the body, that are C-14 and RB-87, etc. but they do not have any significant effect because they don’t emit any gamma radiations, and the radiation emitted by K-40 interact with outer atoms which generate the photoelectric effect.