Background Radiation from Cosmic Rays and Radioactive Nuclei in Our

Multiple Choice

Background radiation from cosmic rays and radioactive nuclei in our surroundings is about 0.13 rem/year. Suppose we assume this all comes from cosmic rays which have an RBE factor of 1.0. The RBE factor for the most dangerous types of radiation is 20. How many rads of the most dangerous radiation could a 100-year-old person have been exposed to in her lifetime without having gone over the recommended limit of 0.5 rem/year?

A) 0.37
B) 0.50
C) 1.85
D) 13
E) 37