Flashcards in Unit 1 Deck (47):
Which wave oscillates at 90* to the motion of travel?
Which wave oscillates at 180* to the motion of travel?
Define the frequency of a wave
The number of waves that pass per unit of time
What is diffraction?
The bending of waves around an object or through an opening
Will a shorter wavelength diffract more or less than a longer wavelength?
Will a wavelength diffract more through a wider opening compared to a narrower opening?
No it will diffract more through a narrower opening
Name the electromagnetic spectrum from longest wavelength to shortest
Radio waves, microwaves, infrared, visible light, UV, X-rays, gamma rays
Do all waves in the electromagnetic spectrum travel at the same speed?
Yes they all travel at the speed of light, 3 x 10^8
What do all the electromagnetic groups have that is different?
Give a use of radio waves
Give a use of microwaves
Give a use of infrared
Give a use of visible light
Give a use of UV
Give a use of X-rays
To see your bones inside your body
Give a use of gamma rays
Killing cancer cells
What type of wavelength has the highest amount of energy?
EG - gamma rays
What is refraction?
The changing of speed as light passes from one material to another
All angles should be measured from where?
The normal, an imaginary line at 90* to the surface
What is the name of the light striking the surface?
What is the name of the ray of light passing through the material?
What is meant by the term 'critical angle'?
It is the angle at which total internal reflection occurs, if the angle is increased further
What does total internal reflection mean?
Light is reflected off of the inside of the material at the same angle it was incident at
What are the three main types of nuclear radiation?
Alpha, beta and gamma
What is the minimum blockage of alpha?
A sheet of paper
What is the minimum blockage of beta?
A few mm of aluminium
What is the minimum blockage of gamma?
A few cm of lead
Which type of radiation is the most ionising?
What is meant by the term 'ionisation'
It is the gain or loss of electrons from atoms, turning them into charged ions
Where does background radiation come from?
Cosmic rays, human body, radioactive gas, rocks, soil and buildings
What is activity?
The number of decays per unit time
What is activity measured in?
Bequerels, 10Bq means that 10 decays have occurred per second
What is absorbed dose?
The energy absorbed per unit of mass
All waves transfer what from one place to another?
What is absorbed dose measured in?
Greys, 80 mGy means that 80 mJ have been absorbed per kilogram
What is equivalent dose rate a measure of?
The biological effect or damage a type of radiation may cause
What is equivalent dose measured in?
Sieverts, H = Dwr
What does the overall risk from exposure depend on?
The equivalent dose, type of radiation, type of tissue involved
What is 'half-life'?
The time taken for the activity to reduce by half
How could you measure the half life of a radio active material?
Background counts must be found first. This is taken away from the counts with the source present. A graph of corrected count against time is plotted
What happens in nuclear fission?
A large nucleus will split into small nuclei. This releases energy and possible more neutrons. Can be spontaneous or induced by using a neutron bombardment
What happens in a nuclear power station?
Nuclear fission is used. Energy held by Uranium is realised during fission to produce heat. Heat absorbed by CO2 gas. The heat is passed onto water to turn into steam which turns a steam turbine. Spinning motion produces electrical energy
What happens in nuclear fusion?
Small nuclei will join together to form a larger nucleus. This will release energy
What can radioactivity be used for?
To sterilise medical equipment
Why must gamma radiation be used to treat cancer?
It is the only type of radiation that can pass through the human body
What can used to find blockages inside the human body?
A medical tracer that emits gamma rays