6.4.2.1 Radioactive Decay and Nuclear Radiation Flashcards
1
Q
What is radioactive decay?
A
- unstable isotopes/atomic nuclei give out radiation and decay into other elements to become more stable
2
Q
What is ionising radiation?
A
- radiation that knocks electrons off atoms, creating positive ions
3
Q
What is ionising power of a radiation source?
A
- how easily a source can knock electrons off
4
Q
What is activity?
A
- rate at which a source of unstable nuclei decays
5
Q
What is activity measured in?
A
- becquerels
- Bq
6
Q
What is count-rate?
A
- number of decays recorded each second by a detector (e.g. Geiger-Muller tube)
7
Q
What nuclear radiation may be emitted?
A
- alpha particle (α)
- beta particle (β)
- gamma ray (γ)
- neutron (n)
8
Q
What does an alpha particle consist of?
A
- two neutrons
- two protons
- (same as a helium nucleus)
9
Q
What is a beta particle?
A
- high speed electron ejected from nucleus as a neutron turns into a proton
10
Q
What is a gamma ray?
A
- electromagnetic radiation from nucleus (short wavelength)
11
Q
How is an alpha particle limited?
A
- cannot penetrate far into materials
- only travel a few cm in air
- absorbed by sheet of paper
12
Q
How is a beta particle limited?
A
- penetrate moderately far into materials
- have a range in air of a few metres
- absorbed by a sheet of aluminium (5mm)
13
Q
How is a gamma ray limited?
A
- absorbed by thick sheets of lead or metres of concrete
14
Q
Why is an alpha particle strongly ionising?
A
- their size
15
Q
Why is a beta particle moderately ionising?
A
- can penetrate moderately far into materials before colliding
