Physics 2.8 Half-Life

Define the half-life of a radioactive isotope

The time it takes for the number of unstable nuclei in a substance to halve
The time it takes for the count rate from a sample to fall to half its initial level

Why are isotopes with long half-lives particularly harmful

They remain radioactive for much longer periods of time
They must be stored in specific ways to avoid humans and the environment from being exposed to radiation for too long

State two uses of nuclear radiation in the field of medicine

Examining of internal organs
Controlling and destroying unwanted tissue

Describe the nature of radioactive decay

Random
Which nuclei decays and when is determined only by chance
It is impossible to predict which nuclei will decay and when

Explain how to determine and verify half-life from a decay curve

Read off the time axis the time it takes for the number of unstable nuclei to half
To verify check that the time it takes for that number to half again is the same

Explain the basic idea behind carbon dating

All living things contain the same relative amount of carbon-12
When they die the carbon decays at a known rate
By measuring the amount of carbon remaining the age can be calculated

Explain how a medical radioactive tracer is used

The tracer is inserted in the body often through the bloodstream
The tracer is radioactive so decays
A detector outside the body can detect this radiation and locate the tracer

What can be said about the half-life of a given radioactive isotope

It is constant

Define the activity of an unstable nucleus

Activity is the rate at which a source of unstable nuclei decays

What is the unit of radioactive activity

Becquerel (Bq)