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Alpha Radiation Range in Air
A teacher measured the count rate at different distances for each of two radioactive sources, A and B.
Figure 15 shows the results.
Explain how Figure 15 shows that Source A only emits alpha radiation.
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Marking points
- 1 Reads from Figure 15 that Source A's radiation travels about 3 cm in air.
- 2 States that the count then falls to the background level.
- 3 Links this short range/low penetration to alpha radiation.
Full-mark answer
The dashed line for Source A falls to the background count rate after about 3 cm. Alpha radiation has only a very short range in air, whereas beta and gamma travel much farther, so Source A only emits alpha radiation.
Why this answer loses marks
The count rate falls, so it must be alpha.
Use the distance where the count reaches background, then link that short air range to alpha penetration.