Chapter 25 - Radioactivity Flashcards
Alpha radiation
Positively charged He nucleus, +2e
Beta radiation
Fast moving electrons (β-) or positrons (β+).
Gamma radiation
High energy photons with wavelength less than 10 to the -13 m. Travel at the speed of light, no charge.
Effect of electric/magnetic field on gamma rays.
Undeflected as they have no charge.
Effect of electric/magnetic field on beta radiation.
Paths of β- and β+ are mirror images.
Effect of electric/magnetic field on alpha radiation.
Deflected less due to greater mass.
Safety when handling radioactive materials?
Handle source with tongs, minimise exposure time and store in lead-lined container.
Nature of radioactive decay.
Random and spontaneous.
Half-life (of a radioactive substance)
Average time taken for half the number of active nuclei in the sample to decay.
Activity (in Bq)
The rate at which nuclei decay.
How can you find the decay constant of a substance using its half-life?
λ = ln2/half-life
What is carbon dating?
When organism dies, it stops taking in carbon-12 but the radioactive isotope carbon-14 continues to decay.
Ratio of C-12:C-14 decreases over time.
Therefore time since the organism died can be determined by comparing ratio in dead and similar living material.
Can you use carbon dating to date rocks?
No, as C-14 half-life is too short so Rb-87 is used instead.
