Edexcel International A Level Physics

Topic Questions

Radioactivity Decay

1
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1 mark

A detector and counter were placed near a radium source. A student measured the count for one minute. He used this value to calculate the count rate in Bq from the source.

Which of the following would increase the accuracy of the student’s value for the count rate?

  • Adding the background count rate to the measured count rate.

  • Increasing the counting time to 10 minutes.

  • Repeating the count with a different detector and calculating a mean value.

  • Subtracting the background count from the measured count.

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2
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Cancer cells inside the body can be killed by directing narrow beams of radiation from different directions onto the cells. The source of radiation is outside the body.

Which radiation would be the most suitable to use?

  • alpha radiation because it is very ionising

  • alpha radiation because it is very penetrating

  • gamma radiation because it is very ionising

  • gamma radiation because it is very penetrating

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1
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Tritium is a radioactive isotope. Wine may contain traces of tritium. One 25‐year‐old bottle of wine was found to have an unusually high activity of 22 Bq.

half-life of tritium = 12.5 years

Which of the following gives the activity of this wine when it was bottled?

  • 44 Bq

  • 66 Bq

  • 88 Bq

  • 110 Bq

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2
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A student investigates the absorption of gamma radiation by lead. She determines the background radiation count rate before she starts the investigation.

Which of the following would not affect her value for the background count rate?

  • the place where she made the measurement

  • the temperature of the surroundings

  • the time interval for the background count

  • the type of radiation detector she used

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3
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Polonium‐218 is a naturally occurring radioactive isotope with a half-life of 185 s.
A sample of this isotope contains 2.75 × 1015 unstable nuclei.

Which of the following expressions can be used to determine the activity in Bq of the sample?

  • fraction numerator 185 over denominator l n space 2 end fraction cross times 2.75 cross times 10 to the power of 15

  • fraction numerator 2.75 cross times 10 to the power of 15 over denominator l n space 2 cross times 185 end fraction

  • fraction numerator l n space 2 over denominator 185 end fraction cross times 2.75 cross times 10 to the power of 15

  • fraction numerator l n space 2 over denominator 2.75 cross times 10 to the power of 15 end fraction cross times 185

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