Radioactive Half Life

What is a becquerel (Bq)?

• One decay per second

• One decay per minute

• One decay per hour

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NGSS.HS-PS1-8

What is the half-life of a radioactive isotope?

• The time taken for the daughter nuclei to increase

• The time taken for the nucleus to decay

• The time taken for half the parent nuclei to decay

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NGSS.HS-PS1-8

Which radioactive isotopes is most suitable tracer to monitor blood flow in a heart?

• Americium-237

  alpha , and a half-life of 78 minutes

• Technetium-99m

  gamma, and a half-life of 6 hours

• Krypton-78

  beta and a half-life of 10.7 years

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NGSS.HS-PS1-8

A radioactive source’s activity falls from 128 Bq to 8 Bq in 20 hours. What is it's half-life?

• 5 hours

• 10 hours

• 30 minutes

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NGSS.HS-PS1-8

Which isotopes would be used in a machine for measuring paper thickness?

• An alpha source with a short half-life

• A beta source with a long half-life

• A gamma source with a long half-life

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NGSS.HS-PS1-8

What percentage of a polonium sample will remain after three half-lives?

• 6.25%

• 12.5%

• 25%

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NGSS.HS-PS1-8

Living wood has a ¹⁴C activity of 120 Bq. Ancient wood has an activity of 30 Bq. The half-life of ¹⁴C is 5,730 years. Estimate the age of the ancient wood.

• 5,730 years

• 11,460 years

• 17,190 years

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NGSS.HS-PS1-8

What isotope should be injected directly into cancer to treat it ?

• An alpha emitter with a short half-life

• A beta emitter with a short half-life

• A gamma emitter with a short half-life

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NGSS.HS-PS1-8

What is the best radioactive source for measuring the amount of crisps poured into packaging?

• A gamma source with a short half-life

• A beta source with a long half-life

• An alpha source with a short half-life

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NGSS.HS-PS1-8

A radioactive substance has a half-life of 30 minutes.

What fraction of the atoms will not have decayed after 1 hour?

• 1/2

• 1/4

• 1/3

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NGSS.HS-PS1-8