Radioactivity Flashcards
Describe the results of Rutherford plum pudding model
Most alpha particles past straight through (atom is mostly empty space)
A small amount were deflected by a large angle (atom is positively charged)
Few particles were deflected back by more than 90 degrees (centre was dense and small)
How can you identify different types of radiation (used to measure thickness of materials)
Through their penetration power as you can check the count rate if you place a sheet of paper or aluminium or concrete between a source and detector
What is the use of gamma radiation
As it is weakly ionising and highly penetrative
- it is used as a detector to help diagnose patients
- used to sterilise equipment by killing bacteria
- used in radiation therapy to kill cancer cells
What is the inverse square law for radiation
Intensity = k/x^2
What are the safety measure with dealing with radioactive sources
- long handled tongs
- lead lined containers
- keep source far
- never point source towards others
When measuring radiation what must you take into account
Background radiation
therefore: corrected rate = total - background rates
Name some sources of background radiation?
Nuclear weapon testing
Cosmic rays
Rocks
What is the decay constant
The probability of a nucleus decaying per unit time
Equation for decay constant
Change in nuclei number/change in time = -decay constant * Initial number of nuclei
Equation for half life
T1/2 = ln(2) / decay constant
What is activity
Activity is the number of nuclei that decay per second
What can half life be used for
Dating of objects
Medical diagnosis - used in medical tracers if they have short half lives in order to limit exposure.
Why might a nucleus become unstable
Too many neutrons
Too many protons (decays via beta plus and electron capture)
Too many nucleons (decays via alpha)
Too much energy (decays via gamma)
Beyond 20 neutrons and protons why does the graph not increase uniformly
As electromagnetic repulsion becomes stronger than strong nuclear force, more neutrons are needed to distance the protons and decrease electromagnetic if force hence keeping the nucleus stable
What is emitted to reach ground state when excited (too much energy)
Gamma radiation
