Section 7 - Nuclear Physics Flashcards
Radioactivity Nuclear Energy
What are the three types of radiation?
Alpha
Beta
Gamma
What is the chance of an alpha particle being deflected passing through a foil of n layers?
1/10000n
How far can alpha radiation travel in air, why?
A few cm
Strongly ionising
How far can beta radiation travel in air, why?
A metre
Weakly ionising
Why does gamma radiation have such a weak ionising effect?
Photons carry no charge
Less effect than alpha or beta
Describe the particle tracks for alpha and beta in a cloud chamber
Alpha: straight tracks
Beta: wispy tracks
What is the count rate?
Number of counts per second
What must be measured first before a source’s count rate is tested?
Background radiation
How do the types of radiation differ with absorption?
Alpha is absorbed by paper
Beta is absorbed by metal foil
Gamma is reduced by several cm of lead
What is contained in a Geiger-Muller tube?
Argon gas at low pressure
What is the purpose of the thin mica window in a Geiger-Muller tube?
Allows alpha and beta particles to enter the tube
What runs down the middle of the Geiger-Muller tube?
A metal rod at a positive potential
What happens when a particle of ionising radiation enters the GM tube?
Particle ionises gas atoms along its track
Negative ions attracted to the rod
Positive ions attracted to the wall
Ions produce further ions
How is a count recorded?
Ions cause a pulse of charge to pass round the circuit through a resistor
Pd pulse across resistor
Recorded as a count
How do the radiation types deflect in a magnetic field?
Alpha and beta deflect in opposite directions
Beta deflects more than alpha
Gamma is not deflected
