Briefly describe the adverse effects caused by exposure to radiation.

The best means of personal protection from radiation for emergency responders is the implementation of three basic principles: time, distance and shielding. Please show your work when answering the following questions:
Using the inverse square law of radiation, what Geiger counter reading would you get for a radioactive material when you are 3 feet from the source (assume an initial reading of 6300 R at a distance of 1 foot from the source)?

b. Dr. Brown has a radioisotope source containing 1.2 x 106 (also written as 1.2E+06) atoms of Plutonium-238 in 1985, how many atoms will remain in 352 years?

c. How many protons and neutrons are present in the plutonium-238 nucleus?

200 word minimum, APA guidelines and formatting, all references and citations listed.

Briefly describe the adverse effects caused by exposure to radiation. Include some specific exposure levels associated with these significant health effects. Lastly, give some examples of measured radiation levels associated with the Three Mile Island incident in the U.S. and in the Chernobyl incident in the Soviet Union. Provide your reference source(s). (Wikipedia is not an accepted reference source.)