<prompt> Thickness of lead apron to prevent radiation -1 mm3 mm0.5mm7mm  <response>: 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 