By applying the inverse square law here, with an initial reading of 6300R at a distance of 1 foot, then at 3 foot after applying the inverse square law of radiation i.e. I=Io/r2, the Geiger Counter would show a reading of 700R. A unique characteristic of radioactive elements is that they continue to emit radioactive rays which causes them to decay. Time after which the number of atoms of a radioactive substance are reduced to half is known as Half-Life. The half-life of plutonium is around 87.7 years. So if Dr. Brown has 1.2 x 106 atoms of plutonium in 1985, we can calculate the number of atoms of plutonium after 352 years to be 74292.Plutonium-238 is a radioisotope which has an atomic number of 94. Now we know that the atomic number of an element identifies its protons and electron so the number of protons in Plutonium-239 is 94. Atomic weight of plutonium-238 is 238 and atomic weight is a sum of protons and neutron. So to find the number of neutrons we would have to subtract number of protons i.e. 94 from the atomic weight i.e. 238 and we would get 144 which is the number of neutrons in plutonium 238.

Ans. Different levels of exposure to radiation have different effects on the human body for example, radiation levels of 10-50 cause nausea, vomiting and alters blood chemistry whereas levels higher than this such as 55-75 lead to nausea, vomiting, hair loss, fatigue and weakness. When the level of radiation is increased at 90-100 the effects become a little dangerous such as hemorrhage. On further increase in the level of radiation such as 100-400, a person may even die with complications of severe hemorrhage. 1000 level of radiation would prove fatal with internal bleeding, rupture of the internal lining of the GIT, and would eventually cause death. CNS breakdown with destruction of neurons is observed on an exposure to the level of 2000 or more (epa.org). The incidents of Chernobyl and Three Mile Island in the years 1986 and 1979 provide us
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