RADIATION Flashcards
(34 cards)
What is radioactive decay?
When unstable nuclei emit radiation in the form of high- energy waves or particles in order to become more stable
Radioactive decay is a _____ process
Random
What’s an alpha particle
A helium nucleus
What’s a beta particle
An electron
What happens when a beta particle is emitted?
A neutron in the nucleus is turned into a proton and an electron (which is then emitted), and the proton remains, increasing the atomic number by one
ALPHA penetrating power
Low: stopped by paper
BETA: penetrating power
Moderate: stopped by a sheet of aluminium
GAMMA: penetrating power
HIGH: only stopped by a few cm of lead, or a couple metres of concrete
ALPHA: ionising ability
High
GAMMA: ionising ability
Low
BETA: ionizing ability
Moderate
WHAT IS IONIZATION
When radiation has enough energy to break an electron away from an atom
How do radiation badges detect levels of radiation?
Radiation badges contain photographic film that turns darker when it absorbs radiation, the badges have different materials of aluminium, lead, paper and plastic that the radiation must penetrate to reach the film- this provides an accurate measure of the dosage received
How do Geiger-muller tubes detect radiation?
-each time it absorbs radiation, it transmits an electrical pulse to a counting machine
-this makes a clicking sound or displays the counting rate each time the tube is absorbing radiation
-the higher the count rate, or the greater the frequency of clicks, the more radiation the tube is absorbing
-it depend son how close the source is to the tube
Natural sources of background radiation (2):
1) RADON GAS from rocks and buildings, there are natural occurrences of uranium in rocks, soils and bricks, the uranium decays as radon gas.
2) COSMIC RAYS FROM SPACE- the sun emits protons continuously, released as high-speed, high-energy particles that collide into molecules in the air’s atmosphere and cause gamma radiation, another source from space is supernovae
Artificial sources of background radiation:
1)nuclear accidents
2) fallout from nuclear weapons
3) nuclear medicine (e.g CT scans, X-rays)
How to account for background radiation in practicals?
Measure the count rate without the source and subtract this from the count rate with the source: corrected count rate
Define activity
The rate at which the unstable nuclei decay
What’s a Bq
Becquerel- one nucleus decaying per 1 second
DEFINE: half-life
The time it takes for the activity of a sample to fall to half of it’s original value
Uses of radiation:
How does alpha radiation work in smoke detectors?
1) alpha emitters in the detector, ionize air and create a current across the circuit
2) when smoke fills the detector, the alpha emission is blocked, and the current is broken,
3) the alarm is triggered when the sensor no longer detects alpha
How does gamma radiation work in RADIOTHERAPY
Gamma radiation is used to treat cancer patients:
1) the high-energy gamma rays, can ionize and kill cells- such as cancerous cells and bacteria because they can penetrate through the body
2) the gamma rays are beamed at the tumour but is moved around the person, to minimize damage to healthy cells but still target the tumour
3)
