Radioactivity. Some substances are radioactive . Their atoms release some of this energy as radiation. Radioactivity.
Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.
Some substances are radioactive. Their atoms release some of this energy as radiation
Radiation in the environment and is caused by the radioactive in rocks, the air and our bodies, and also from cosmic rays from outer space we called it as “Background Radiation”.
Gold Leaf electroscope
Geiger Muller Tube
Diffusion Cloud Chamber
> Helium Nucleus ( 42He)
> Positive Charge
> high mass
> a few centimeters range in air
> slight deflection in electric/magnetic fields.
> strong ionization
> can be stopped by thin paper
> Pure source: Americium (Am-241)
> High-energy electron (0-1e)
> Negative Charge
> low mass
> a few meters range in air
> great deflection in electric/magnetic f.
> weak ionization
> can be stopped by aluminium (5mm)
> Pure source: Strontium (Sr-90)
> High-energy electromagnetic radiation
> zero mass
> a few hundred meters range in air
> none deflection in electric/magnetic field.
> very weak ionization
> can be stopped by thick lead or concrete
> source: Cobalt (Co-60) covered by aluminium
A radioactive source has a half-life of 10 minutes. What fraction is left in 1 hour?
Carbon-14 has a half-life of 5700 years. A 10 g sample of wood cut recently from a living tree has an activity of 160 counts/minute.
A piece of charcoal taken from a prehistoric campsite also weight 10 g but has an activity of 40 counts/minute. Estimate the age of the charcoal.
The ratio of the number of atoms of argon-40 to potassium-40 in a sample of radioactive rock is 1 : 3.
Assuming that there was no potassium in the rock originally and that argon-40 decays to potassium-40 with a half life of 1500 million years, estimate the age of the rock.
4. Radioactive Uranium-238 (U, proton number 92) decays to thorium (Th), emitting an alpha particle and gamma rays. Show this decay reaction as a nuclide equation