Relatifity

A radioactive source produces a count rate on a detector of 1600 counts / s.

After 32 hours the count rate has fallen to 100 counts / s.

Both count rates have been corrected for background radiation.

What is the half-life of the source?

2.0 hours B 6.4 hours C 8.0 hours D 16 hours

• 2,0 hours

• 6,4 hours

• 8,0 hours

• 16 hours

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

• 125 decays/s

• 250 decays/s

• 500 decays/s

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/s

• 123 counts/s

• 134 counts/s

• 167 counts/s

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?

• 0 mg

• 40 mg

• 100 mg

• 200 mg

The counter of a radiation detector placed close to a radioactive source gives a count rate of 1600 counts / s.

The half-life of the source is 1 week.

Ignoring background radiation, calculate the count rate 1 weeks after the first measurement....

• 800 counts / s

• 200 counts / s

• 400 counts / s

• 100 counts / 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

• 20 min

• 40 min

• 60 min

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 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 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