radioactivity Flashcards
how should the scientist correct the count rate of the radioactive isotope for background radiation
subtract the background count rate
what is an alpha particle
a helium nucleus
two protons and two neutrons
which two types of radiation can be affected by a magnetic field
alpha
beta
what is a beta particle
fast moving electrons produced when a neutron changes into a proton and an electron
what is a gamma ray
an electromagnetic wave
what is the charge of a gamma ray
0
what is the charge of a beta particle
-1
what is the penetrating power of an alpha particle
stopped by paper
what is the penetration power of a beta particle
stopped by a few mm aluminium
what is the penetration power of a gamma ray
gets stopped by a lot of cm of lead or many meters of concrete
what happens to a particle when it is ionised
its number of electrons changes which gives it a charge
what are the ionising powers of the three different types of radiation
alpha - most ionising
beta
gamma - least ionising
what happens to the mass and proton numbers during gamma decay
they remain the same, the process just makes the nucleus less energetic
what is a sievert
the amount of radiation received by a person (the dose)
IN WHAT TWO WAYS CAN RADIATION BE MEASURED AND DETECTED
using a photographic film or a geiger-muller tube
how does photographic film show radiation
it becomes darker as it absorbs radiation
the darker it is, the more radiation it has absorbed
how is photographic film used in real life situations
people who work with radiation such as radiographers wear film badges which are checked regularly to monitor levels of radiation absorbed
to get an accurate measure of the dose received, the badge contains different materials that the radiation must penetrate in order to reach the film
how does a geiger-muller tube measure radiation
each time it absorbs radiation, it transmits an electrical pulse to a counting machine which makes a clicking sound or displays the COUNT RATE
how does distance from a radioactive object affect the amount of radiation present
it decreases with distance because the waves spread out
natural sources of radiation
- rocks and building materials
- cosmic rays from space
- foods
man made sources of radiation
- medical sources
- nuclear waste/accidents
what percentage of activity would a radioactive source be at after two half lives
25% (halving twice 100 - 50 then 50 - 25)
