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A Level Physics Tutor

Inverse Square Law

Introduction
 

The inverse square law describes how the intensity of radiation decreases as the distance from a point source increases. As radiation spreads out uniformly in all directions, the same energy is distributed over an increasingly larger area, causing the intensity to fall rapidly with distance. This principle is widely used in nuclear physics, astronomy and radiation safety.
 

AQA A Level Physics Specification: 3.8.3 Inverse Square Law
 

What You Need to Know
 

  • State the inverse square law for radiation from a point source.

  • Explain why the intensity of radiation decreases with increasing distance.

  • Understand that intensity is inversely proportional to the square of the distance from the source.

  • Apply the inverse square law to calculate changes in radiation intensity.

  • Explain why count rate decreases with distance from a radioactive source.

  • Correct count-rate measurements for background radiation where appropriate.

  • Solve quantitative problems involving radiation intensity and distance.

  • Apply the inverse square law to practical situations involving radioactive sources.
     

Downloadable Topic Pack

 

Inverse Square Law Topic Pack Exam Questions and Answers
 

 

This downloadable resource contains carefully selected AQA A Level Physics exam questions covering the inverse square law, radiation intensity, count rate, background radiation and distance calculations, together with fully worked solutions designed to strengthen understanding and improve exam performance.
 

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