Phy Y10Y11 Y11 C23 IGCSE C23.3 Physics: half life 2025J

A powder contains 400mg of a radioactive isotope that emits α-particles. The half-life of the isotope is 5 days. What mass of this isotope remains after 10 days?

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A powder contains 400mg of a radioactive isotope that emits α-particles. The half-life of the isotope is 5 days. What mass of this isotope remains after 10 days?

• 0mg

• 40mg

• 100mg

• 200mg

The reading on a detector placed near a radioactive material is 536 counts per second. The background count rate is 44 counts per second. The half-life of the radioactive material is 34 hours. What is the reading on the detector after 68 hours?

• 44 counts per second

• 123 counts per second

• 134 counts per second

• 167 counts per second

The graph shows how the decay rate of a radioactive source changes with time. What will be the decay rate at 8 days?

• 0 decays / s

• 0 125 decays / s

• 250 decays / s

• 500 decays / s

A reading is taken every 10 minutes of the number of emissions per second from a radioactive source. The table shows the readings.

What is the half-life of the source?

• 10 min

• 20min

• 40min

• 60 min

The graph shows the activity of a radioactive source over a period of time.

What is the half-life of the source?

• 1 hour

• 1 2 1 hours

• 3 hours

The graph shows how the count rate on a detector due to a radioactive source changes with time.

What is the count rate at 5.0 hours?

• 960 counts per minute

• 600 counts per minute

• 150 counts per minute

• 0 counts per minute

The half-life of a radioactive substance is 10 minutes. A sample of the radioactive substance contains 2000 nuclei. How many radioactive nuclei were in the sample half an hour earlier?

• 250

• 4000

• 6000

• 16000

The count rate from a radioactive isotope is recorded every hour. The count rate is corrected for background radiation. The table shows the readings

What estimate of the half-life of the isotope can be obtained from the readings in the table?

• between 1 and 2 hours

• between 2 and 3 hours

• between 3 and 4 hours

• between 4 and 5 hours

The table shows the results of an experiment to find the half-life of a radioactive substance.

What is the half-life of the substance?

• 60 seconds

• 120 seconds

• 180 seconds

• 240 seconds