5.1.1- Radioactivity And Nuclear Energy Flashcards
What principle can you use when calculating the closest approach of a scattered particle deflected by 180°
That the initial kinetic energy equals the final electric potential energy
Why is electron diffraction more accurate than alpha particle scattering
As electrons are leptons they do not interact with the strong nuclear force where as neutrons and alpha particles do
How is this electron diffraction different to the AS level syllabus
At AS-level the electrons defected through the gaps between the atoms however hear the electrons diffract around an individual nucleus. This is why Lambda must be near the diameter of the nucleus for maximum diffraction.
How do you convert electron volts (eV) to Joules
Multiply by the charge of an electron (1.6x10^-19)
What is the equation for where the first minimum appears with electron diffraction which can be used to work out the diameter of the nucleus.
Sinø= 1.22 x wavelength/diameter
What is the typical radius of an atom
1x10^-10 m
What is the typical radius of a nucleus
1x10^-15 m
What is the constituent part of Gamma radiation
Sort-wavelength, high-frequency electromagnetic wave
Why is u (atomic mass units) used when referring to masses
To simplify things, one atomic mass unit is equal to 1.661×10^-27 kg, about the mass of a proton or neutron.
What is the penetrating power of alpha particles
Absorbed by paper or a few centimetres of air
What is the penetrating power of beta minus radiation
Absorbed by around 3 mm of aluminium
What is the penetrating power of beta plus radiation
Annihilated by electron so virtually zero range
What is the penetrating power of gamma radiation
Absorbed by many centimetres of lead, or several metres of concrete
What are the conclusions from Rutherford scattering
The nuclei must be positive to repel alpha particles, they must be very small as very few are deflected by big angles, and most of the mass and positive charge must be contained within a small nucleus as most just pass straight through. (TL:DR- small, positive nucleus with lots of empty space)
Name five sources of background radiation
- The air- Radon gas released from rocks (largest contributor)
- Ground and buildings- the rocks they contain
- Cosmic radiations- cosmic rays are high energy particles from space that collide with particles in the upper atmosphere producing nuclear radiation
- Living things- radioactive Carbon-14
- Man made- medical and industrial sources
What is the decay constant
The probability of an atom decaying per unit time
What is the activity of a sample
The number of atoms that decay each second, measured in Becquerels (Bq)
Is also equivalent to the the rate of change of unstable nuclei.
What is the half life of a substance
The average time it takes the number of unstable nuclei to halve
Name two uses of radioactive isotopes
- Radiocarbon dating using Carbon-14
2. Medical radioactive tracers- show tissue/organ functions
State 4 problems with radiocarbon dating
- Can only find age of material, not the object
- Uncertainty in the amount of C-14 that existed thousands of years ago
- Small sample size so statistically unreliable
- May have had contamination with other radioactive sources.
In what type of nuclei does Alpha mission
V.heavy nuclei
In which type of nuclei does beta minus decay occur
Neutron rich
In which type of nuclei does beta plus decay occur
Proton rich
In which type of nuclei does gamma emission occur
Too much energy/excited
Also caused by electron capture
