Worksheet: Ionizing Radiation

In this worksheet, we will practice relating the interactions of types of ionizing radiation to their absorption by thicknesses of different density materials.


One half the 𝛾-rays from a 99mTc sample are absorbed by a 0.170-mm-thick lead shielding layer. Half of the 𝛾-rays that pass through the first layer of lead are absorbed in a second layer of equal thickness. What thickness of lead will absorb all but one in 1,000 of these 𝛾-rays?


A sodium iodide crystal of thickness 2.00 cm absorbs all but 10.0% of rays from a radioactive source. What percentage of rays will not be absorbed by 4.00 cm thickness of the same material?

  • A3.33%
  • B5.00%
  • C1.00%
  • D2.50%
  • E6.93%


What is the dose in millisieverts for a 0.1 Gy X-ray?


A 2.50 cm thick piece of lead can absorb 95.0% of the rays from a radioactive source. How many centimeters of lead are needed to absorb all but 0.150% of the rays?

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