Radiology · Fundamentals of X-Ray, CT, MRI and USG (Physics, Basics)

According to the inverse square law, if the distance from a point X-ray source is doubled, the intensity of the beam becomes:

  • A One-fourth the original intensity
  • B One-half the original intensity
  • C One-eighth the original intensity
  • D Unchanged
Correct answer: A. One-fourth the original intensity

Explanation

The inverse square law states that intensity is inversely proportional to the square of the distance from the source. Doubling the distance reduces intensity to 1/4 (1/2²). This principle is fundamental in radiation protection and radiographic technique.

Reference: Radiologic Science for Technologists, 12th ed.

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