Section 3- Radioactivity And Astronomy Flashcards
Relative mass of a proton
1
Relative mass of a neutron
1
Relative mass of an electron
0.0005
Relative charge of a proton
+1
Relative charge of a neutron
0
Relative charge of an electron
-1
What does it mean if an atom is ionised?
It has lost an electron
Isotopes
Isotopes of an element are atoms with the same number of protons but a different number of neutrons
Half-life
The half-life is the average time taken for the number of radioactive nuclei in an isotope to half
Nuclear fission
Nuclear fission is a type of nuclear reaction that is used to release energy from uranium atoms
Sources of background radiation
- in the air
- some foods
- rocks
- building materials
Uses of radiation
- fire alarms
- sterilising medical equipment
- fresh fruit
Dangers of radiation
- can enter living cells and ionise atoms and molecules within them. This can lead to tissue damage
- radiation sickness (leads to vomiting, tiredness and hair loss)
- cancer
Nuclear Fussion
Nuclear fusion is the opposite of nuclear fission. In nuclear fusion, two light nuclei collide at high speed and join (fuse) to create a larger heavier nucleus
Why does nuclear fusion only only occur at high temperatures?
This because the positively charged nuclei have to get very close to fuse so the strong force due to electrostatic repulsion has to be overcome (10 000 000 °c)
Pros and cons of nuclear power
-dangerous
-difficult to dispose of as it has very long half lives
-can cause pollution
-high cost
+generally safe
+reliable
+doesn’t release greenhouse gases
+huge amounts of energy can be generated
How do PET scans help diagnose illness?
By showing tissue or organ function
Eg. Active cancer tumours by showing metabolic activity in tissue
Planets
These are large objects that orbit a star.
Dwarf planets
These are planet like objects that aren’t big enough to be planets (eg.Pluto)
Moons
These orbit planets with almost circular orbits
Artificial satellites
Usually orbit the earth in fairly circular orbits
Asteroids
Lumps of rock and metals that orbit the sun. They’re usually found in the asteroid belt
Comets
Lumps of ice and dust that orbit the sun. Their orbits are usually highly elliptical (a very stretched out circle)
some travel from near the sun to the outskirts of our solar system
Red shift
-
Big Bang theory
-
Steady state theory
-
Life cycle of a star
-
Geocentric model
-
Heliocentric model
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