
Concept explainers
(a)
Reason why exposure inversely varies with square of distance from source.
(a)

Answer to Problem 48E
The exposure varies inversely with distance from source because the flux of
Explanation of Solution
Exposure to radiation is defined by extent of dose that is received by matter. The radiation energy is continuously distributed in all direction at a certain distance from radiating source.
The flux of radiation is defined as amount of radiation per unit area per unit time. If a spherical region of radius same as distance from source is imagined, then the flux of radiation inversely varies with distance because area of sphere is directly proportional to square of its radius.
Thus, the exposure which is a measure of flux also varies inversely with square of distance.
Conclusion:
Thus, exposure varies inversely with distance from source because the flux of radiation is inversely proportional to the distance.
(b)
Time required to produce dose of
(b)

Answer to Problem 48E
The time required to produce dose of
Explanation of Solution
A dose of
Write the expression of biologically equivalent dose
Here,
Write the expression of required time for second radium source
Here,
Conclusion:
Substitute
Substitute
Thus, the time required to produce dose of
(c)
Time required to produce dose of
(c)

Answer to Problem 48E
The time required to produce dose of
Explanation of Solution
Write the expression of required time for third radium source
Here,
Conclusion:
Substitute
Thus, the time required to produce dose of
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Chapter 31 Solutions
General Physics, 2nd Edition
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