Physics Flashcards
Sources of background radiation?
Radon gas
Cosmic rays
Food
What happens when polyethene is rubbed with a duster?
Electrons transferred to the rod making it negative
What happens when acetate is rubbed with a duster?
Electrons are transferred from the rod to the duster so the rod becomes positively charged
What are isotopes?
Different number of nuetrons
What is radioactive decay?
Unstable nuclei decay and give out ionising radiation
Random process
Alpha particles
Helium nucleus- 2 nuetrons, 2protons
Weakly penetrating
Strongly ionising as they are big
Blocked by paper
Beta particle?
Fast moving electron from when a nuetron breaks down into a proton and an electron
Moderately penetrating
Blocked my aluminium
Gamma rays
Electromagnetic wave
Very penetrating
Weakly ionising
Blocked by thick lead
What happens during alpha decay?
Atomic number goes down by 2 and atomic pass goes down by 4
What happens during beta decay?
Mass number is unchanged
Atomic number goes up 1
What is half life?
The average time taken for the number of unstable nuclei in a radioactive isotope sample to halve
Count rate to half
Uses of alpha radiation?
Smoke detectors
What is beta radiation used for?
Tracers - see if body absorbs and where
Thickness gauges
Uses of gamma rays
Tracking movement of waste materials (leaks etc)
Radiotherapy
Sterilisation is food and surgical instruments
How does radioactive dating of rocks work?
See how much of radioactive isotope is left and knowing isotope
E.g carbon 14
How does nuclear fission occur?
Absorption of nucleus into uranium or plutonium nucleus = split
Spits out 2/3 nuetrons and lots of energy
=chain reaction
Fusion?
Joining of two nuclei, releasing lots of energy
Needs very high pressure and temperature - can’t build reactor strong enough
How to make helium nucleus via fusion?
1H+2H—
What is anhilkation?
When an electron and an antiparticle collide releasing energy as gamma rays
