Inverse Square Law for Gamma Radiation

Steps:

• Gamma radiation is electromagnetic waves, unaffected by magnetic fields or charges.
• Intensity of radiation decreases with distance squared (inverse square law: I ∝ 1/r²).
• Absorbers like lead reduce gamma penetration, lowering detected counts.
• Closer proximity increases the fraction of radiation reaching the detector.

Why D is correct:

• Moving the detector closer decreases r, so count rate increases per I ∝ 1/r².

Why the others are wrong:

• A: Lead absorbs gamma rays, reducing count rate.
• B: Gamma rays are neutral and unaffected by magnetic fields.
• C: Moving further increases r, decreasing count rate per inverse square law.

Final answer: D