Types of Radiation - Atomic Structure Physics Flashcards
Isotope
Atoms with different number of neutrons
Radioisotope
Isotope that emits radiation because the mass in the atom’s nucleas becomes too heavy. The attraction in the nucleas decreases and becomes unstable
What is the approximate size of an atom?
1 X 10⁻¹⁰
What is the size of a radius of a nucleas?
less than ¹⁄₁₀₀₀₀
What did Ernest expect of the alpha particles when they went through the gold foil?
They would be deflected
What is an alpha particles made from and how?
If the nucleus has too few neutrons, it will emit a ‘package’ of two protons and two neutrons called an alpha particle.
Helium ion, two neutrons, two protons and no electrons.
What is the ionising power of an alpha particle?
Highly ionising due to its size - dangerous if ingested
What is an alpha particle’s range in air?
Less than 5cm
What is the penetrating power of an alpha particle?
Few mm of Skin/paper
What is penetrating power?
How far into a material a radiation will be able to go
What is the mass and atomic number of an alpha particle?
Mass number = 4
Atomic number = 2
(same as Helium)
What does ionising mean?
The ability of a type of radiation to turn an atom into an ion
What is a beta particle?
Fast-moving electron
What forms a beta particle?
If the nucleus has too many neutrons, a neutron will turn into a proton and emit a fast-moving electron
What is the ionising power of beta radiaition?
Moderately ionising
What is a beta particle’s range in air?
1 metre in the air
What is a beta particle’s penetrating power?
3mm aluminium foil
What is gamma radiation?
Waves of electromagnetic radiaiotn
What is gamma radiation?
Waves of electromagnetic radiaiotn
When is gamma radiation emitted?
Emitted by an unstable nucleus of an atom during radioactive decay.
How ionising is gamma radiation?
Weakly ionising
How penetrating is gamma radiaiton?
Highly penetrating
What stops gamma radiation?
Lead/ concrete
What is the range of gamma radiation?
1km
Alpha and Beta radiation
What are the characteristics of alpha and beta particles in terms of their deflection in an electric field?
- Alpha and beta particles are deflected in opposite directions in an electric field
- beta particles are delfected more
- alpha particles have a greater charge than beta but beta have much less mass
- beta have a greater specific charge than alpha
How do smoke alarms work?
- Americium 241 is an isotope that releases alpha particles
- The alpha particles ionise the air
- This created a current between the 2 charged plates
- The alarm won’t sound
- Smoke slows down the ions betweent the 2 charged plates
- This decreases the current
- The current detector detects a decrease and the alarm goes off
How is activity measured?
geiger-muller tube
what is the count-rate?
number of decays recorded each second by a detector
count rate vs activity
count rate can include background radiation
4 types of radiation
alpha, beta, gamma, neutron
whats contamination
unwanted radioactive isotopes end up on other materials
2 natural main sources of background radiation
- Radioactive rock - granite
- cosmic rays from space - v high energy particles whichtravel through space and crash into earths atmos
2 man made sources of back ground radiation
- fall out from nuclear weapons testing - released radioactive isotopes into environment
- nuclear accidents
what is radiation dose measured in?
what is 1mSv = to
sieverts
1mSv = 1/1000 of a sievert
How is nuclear radiation used in medicine
- exploring internal organs
- controlling/destroying unwated tissue
what affects the level of background radiation dose
occupuatioon and location
Conditions of exploring internal organs using a tracer
- tracer must emit radiation that can pass out of body and be detected ( gamma/beta)
- tracer mustnt be strongly ionising - minimise damage
- tracer musnt decay into another radioactive isotope
- tracer must have short half life so not present in body for long time
what is radiotherapy
cancer detroyed using ionising radiaiton
