This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Environment and health, Subject name: Social & Preventive Medicine
Thickness of lead apron to prevent radiation - 
Select and explain. 
A. 1 mm, B. 3 mm, C. 0.5mm, D. 7mm
C: 0.5mm
Answer: C: 0.5mm 
Explanation: lead aprons of thickness 0.5mm will reduce the intensity of scattered X rays over 90% and should be worn by all workers regularly exposed to X ray procedures. Radiation protection is the youngest bramch of hygiene and is called radiation hygiene. Parks textbook of preventive and social medicine.K Park. Edition 23.page no: 745