6. Nuclear Physics Flashcards
What are ‘radioactive’ substances?
Substances which give out radiation from the nuclei of their atoms, all the time, whatever is done to them
What is background radiation and where does it come from?
It is radiation that is constantly around us
It comes from:
Natural sources such as rocks and cosmic rays from space
Man made sources such as fall out from nuclear tests and accidents
What is an Alpha particle?
Two neutrons and two protons, it is the same as a Helium nucleus
What is a Beta particle?
An electron from the nucleus
What is a Gamma radiation?
Electromagnetic radiation from the nucleus
Which substance ionises the most powerfully?
Beta then alpha
Gamma waves not deflected by electric or magnetic fields
How penetrative is alpha radiation?
Not very it can be blocked by paper
How penetrative is Beta radiation?
It can pass through paper but not aluminium
How penetrative is Gamma radiation?
Very can pass through aluminium but is blocked by lead
If the radioactive source is inside the body:
Alpha radiation is the most dangerous because it is easily absorbed by cells
Beta and gamma radiation are not as dangerous because they are less likely to be absorbed by a cell and will usually just pass right through it
If the radioactive source is outside the body:
Alpha radiation is not as dangerous because it is unlikely to reach living cells inside the body
Beta and gamma radiation are the most dangerous sources because they can penetrate the skin and damage the cells inside
What is the definition of half-life?
The average time it takes for the number of nuclei of the isotope in a sample to halve
The time it takes for the count rate from a sample containing the isotope to fall to half its initial level
What is nuclear fusion?
Nuclear fusion is the joining of two atomic nuclei to form a larger one
Nuclear fusion is the process by which energy is released in stars
What do Nuclear Fusion reactions release?
Huge amounts of energy
However not currently a viable method for generating power on Earth
What is one use of alpha radiation?
It is used in smoke alarms
When there is a lot of smoke, the smoke absorbs the radiation so it doesn’t reach the detector and the alarm is triggered
What is one use of Beta radiation is used in industry?
It is used to keep the thickness of paper correct during manufacturing
What is nuclear fission?
Nuclear fission is the splitting of an atomic nucleus, into smaller nuclei and neutrons
What substances are used in Nuclear reactors?
Uranium 235 and plutonium 239
What is the life cycle of stars the same size as our sun?
Protostar Main sequence star Red giant White dwarf Black dwarf
What is the life cycle of stars much bigger than our sun?
Protostar Main sequence star Red super giant Supernova Neutron star / Blackhole
When are stars formed?
When enough dust and gas from space is pulled together by gravitational attraction
Smaller masses may be attracted by larger mass to become planets
Why are main sequence stars stable?
Because the outward force of fusion is balanced by the inward force of gravity
When does the main sequence star come around?
When the Hydrogen nuclei begin to fuse together
What happens when a main sequence star runs out of fuel?
It’s inner core collapses and the outer layers swell and cool
It then either becomes a red giant or red super giant
