Radiation can be measured according to activity, exposure, or its effect on biol

Question

Radiation can be measured according to activity, exposure, or its effect on biological tissue. Units of curies (Ci) and disintegrations per second (dps) measure activity. The rad measures exposure, where rad stands for radiation absorbed dose. The rem measures biological effect, where rem stands for roentgen equivalent man. RBE is a multiplication factor known as relative biological effectiveness and is approximately 1 for beta and gamma radiation and 10 for alpha radiation. The following conversion factors relate these quantities: 1 Ci = 3.7 times 10 10 dps 1 rad = 1 times 10-2 J/Kg tissue number of rems = (RBE) (number of rads) Note that the conversion factors between curies and disintegrations per second and between rads and joules per kilogram of tissue are exact (i.e., they contain an infinite number of significant figures). The RBE, however, is approximate and has only one significant figure because it varies with the dose rate, total dose, and type of tissue affeched. Tests on human subjects along the East Coast of the United States in 1965 and 1966, following the era of atomic bomb testing, revealed quantities of about 1.11pCi of plutonium radioactivity (alpha radiation) in a test subject. A 75-kg person is exposed to this radiation for 1.00 year (365 days). If each alpha particle deposits 8.00 times 10-13 J what is the number of rads absorbed by the person? Express your answer in rads using two significant figures.

Explanation / Answer

As weight of the person is 75 kg so amount of tissue is also 75 kg

amount of radiation = 4.11 *10-2 dps

the person exposes to it is 1 year = 365 * 24 * 60 * 60 =31536000 sec

so total radiation =31536000 * 4.11 *10-2 = 1296129.6

amout of heat per radiation = 8* 10-13 J

so total heat =1296129.6 * 8* 10-13 = 1.036 * 10.-6 J

so amount of rads = 1.036 * 10.-6 J / 75 kg = 1.38 * 10-8 J/ kg = 1.38 * 10-6 * 102 Rads = 1.38 * 10-4 rads

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