Problem from Intro to Health Physics by Cember and Johnson

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SUMMARY

The discussion focuses on solving a problem from "Intro to Health Physics" by Cember and Johnson regarding a He–Ne laser. Key calculations include the time of pupil exposure during each scan, radiant exposure per scan, average irradiance at the cornea, and the appropriate hazard class for the laser. The laser operates at a scanning rate of 10 s−1 with a power output of 5 mW and a beam divergence of 5 milliradians, evaluated at a viewing distance of 200 cm.

PREREQUISITES
  • Understanding of laser physics and safety standards
  • Familiarity with radiant exposure calculations
  • Knowledge of irradiance and its measurement
  • Basic concepts of beam divergence
NEXT STEPS
  • Calculate radiant exposure using the formula: radiant exposure = energy/area
  • Learn about laser hazard classifications as per ANSI Z136 standards
  • Explore the effects of beam divergence on laser safety
  • Study the principles of eye exposure limits for laser radiation
USEFUL FOR

Students and professionals in health physics, laser safety officers, and anyone involved in the assessment and management of laser hazards.

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Hello guys, can you please help me figure out how to solve this problem. Many thanks!

A scanning He–Ne laser that scans at a rate of 10 s−1 emits 5 mW through an
aperture of 0.7 cm. If the beam divergence is 5 milliradian, then, for an intrabeamviewing
distance of 200 cm, calculate
(a) the time during each scan that the pupil of the eye can be exposed,
(b) the radiant exposure per scan,
(c) the average irradiance at the cornea, and
(d) the hazard class that should be assigned to this laser?
 
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