A radiation worker receives an absorbed dose of 1 Gy to the lung from alpha particles (radiation weighting factor 20) and 1 Gy to the whole body from gamma rays (weighting factor 1). If both exposures are considered together, the effective dose is:
- A 21 Sv ✓
- B 2 Sv
- C 40 Sv
- D 2 Gy
Correct answer: A. 21 Sv
Explanation
Equivalent dose equals absorbed dose multiplied by the radiation weighting factor: alpha gives 20 Sv and gamma gives 1 Sv, totalling 21 Sv. The gray measures physical energy absorbed per kilogram, while the sievert incorporates the biological effectiveness of the radiation type, which is why alpha particles are 20 times more damaging per gray. Option D confuses units, and option B ignores the weighting factors entirely.
Reference: Park's Textbook of Preventive and Social Medicine, 27th ed.
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