physics chapter 11 and 8 Flashcards
what are the different types of decay
spontaneous= alpha beta gamma
deliberated decay=neutron+uranium=kr+ba+3n+ energy
reactor
in a reactor there are some rods inured by uranium nuclei and also some other rods made up of graffite known as moderator slowing down high speed neutrons generated as a result of fission process, to start another fission reaction additionally there are some control rods to regulate the rate at which fission reactions happen. they can be lowered down to cover fuel rods then the process will stop meaning reaction has finished.
mechanism of a reactor
neutron is collided with fuel rods( enriched with uranium nuclei ) as a result of this reaction, 3 more neutrons are generated, which are really fast. due to their high speed they cannot handle a new fission reaction so their speed has to be standerdized therefor the other part known as reactor slows down these neutrons to start a new fission reaction. for safety, when the reactions becomes out of control, control rods are designed, they cover fuel rods when neutron is coming to collide with uranium it will be absorbed.
fusion reaction:
two small nucli join together to form a bigger nuclei
- great value of energy is relesed and an initial energy is required to bring those small nuclei close together to join and form a heavier nucleus
- process only happens in stars not on earth
energy+2h+3h=42h+11n+ energy
fission reaction
heavy nucleus breaks down, n+u=kr+br+3n+ energy
difference between fission and fusion
fusion has initial energy, not practical on earth and generally has a lot of energy
evidence for stability of nuclei , binding energy
graph showing binding energy per nucleon number agaist nucleon number
- to reach peak of graph which is 60 and 8, after this a increase in neutron number and decrease in binding energy is observed which shows stability is getting less and less. unstable nuclei are located on the right side of the peak.
evidence for stability, zone of stability graph
line of stability This line runs diagonally through the graph and represents the stable isotopes with balanced proton-to-neutron ratios.
Neutron-Rich Isotopes: Found above the line of stability. These isotopes have an excess of neutrons and are typically beta emitters (
β
−
), where a neutron converts into a proton.
Proton-Rich Isotopes: Found below the line of stability. These isotopes have an excess of protons and are typically positron emitters (
β
+
) or undergo electron capture, where a proton converts into a neutron.
mass defect
when nucleons stick together inorder to form a nucleus they exhibit a lower mass compared to the situation in which they are separated. this difference in mass is known as mass defect. the reasoning behind this phenomena is said to be that mass and energy are interchangable quantities. the lack of mass in the nucleus is said to be due to binding energy which sticks nucleons together.
binding energy: e=mc^2
mass defect=m=m2-m1
half life
is the time taken for an unstable sample to decay to reach the half of initial number of its nuclear
graph:
the graph never crosses the horizontal axis
the only factor effective on half life is collision
beta decay
negative beta decay:
a/zx=a/z+1+-1e+ antineutrino
a neutron in the nucleus is converted into a proton.
positive beta decay:
a/z=a/z-1+e+1+ neutrino
a proton in the nucleus is converted into a neutron.
Mass Number: The mass number remains unchanged in both types of beta decay,
