introduction to radiation
DESCRIPTION
Introduction to Radiation. The classical atom. All radiation is a byproduct of the decay of the atom … specifically the nucleus of the atom. Terminology. Radiation : energy in transit High energy results in ionization Low energy results in non-ionization - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/1.jpg)
Introduction to Radiation
![Page 2: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/2.jpg)
The classical atom
• All radiation is a byproduct of the decay of the atom … specifically the nucleus of the atom
![Page 3: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/3.jpg)
Terminology
• Radiation : energy in transit– High energy results in ionization– Low energy results in non-ionization
• Radioactivity : the characteristic to emit energy capable of ionization
• Ionization : the removal of electrons from an atom (changing the overall charge on the atom) by high energy radiation
![Page 4: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/4.jpg)
3 types of radiation
• Alpha radiation• Beta radiation• Gamma radiation
![Page 5: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/5.jpg)
Alpha Radiation• Occurs when a particle consisting of 2
neutrons and 2 protons is ejected from a nucleus– The ejected particle is essentially the nucleus of a
helium atom
![Page 6: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/6.jpg)
• Alpha decay occurs only in heavy, neutron rich atoms such as Uranium, Thorium and Radium– Neutron rich means that there are many more
neutrons than protons in the nucleus
• 235U92 231Th90 + 4a2
![Page 7: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/7.jpg)
Properties of alpha radiation
• Positively charged• Very heavy• Most energetic of all of the radiation• Can cause many ionizations in a short distance– Travels a few centimeters in air– Stopped by a sheet of paper– Only dangerous if ingested
![Page 8: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/8.jpg)
Applications of alpha radiation
• Smoke detectors– Alpha source ionizes the air to allow for the
passage of small currents through an air gap. Smoke obstructs this flow … setting the alarm off
• Power source– Used in space probes and pace makers
• Ion engines
![Page 9: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/9.jpg)
Beta Radiation
• Ejection of an electron from the nucleus of an atom– How can a nucleus eject an electron?
![Page 10: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/10.jpg)
• The electron is created out of the nucleus for beta decay– The nuclear weak force causes a neutron to decay
into an electron, a proton and an anti-neutrino– 1n0 1p1 + 0e-1 + v-
![Page 11: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/11.jpg)
• Beta decay occurs in neutron rich atoms– A common radiation type in all nuclear reactors– Decay of rhenium into osmium– 187Rh75 187Os76 + 0e-1 + v-
![Page 12: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/12.jpg)
Properties of Beta radiation
• Negatively charged• Nearly massless• React less readily compared to alpha radiation• Can travel several meters in air– Stopped by thin sheets of plastic or metal
• Travels faster than light in certain materials (water) resulting in Cherenkov radiation
![Page 13: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/13.jpg)
![Page 14: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/14.jpg)
Applications of Beta radiation
• Radiation therapy used to destroy cancer cells• Radioactive tracers• Used to check thickness of materials such as
paper
![Page 15: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/15.jpg)
Gamma Radiation• Present in most of the other forms of decay
processes– After a radioactive decay the daughter nuclei is
fairly energetic and will release some of this excess energy as a gamma ray pulse / burst
![Page 16: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/16.jpg)
Properties of gamma radiation
• Similar in nature to light or microwaves– Only higher in energy
• No mass• No charge• Travels at / near the speed of light• Interact through collisions with electrons– Lose energy slowly
• Can travel hundreds of meters in air
![Page 17: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/17.jpg)
Application of Gamma Radiation
• Used in cancer surgery – Gamma ray knife
• Sterilization of food products– Irradiation
• Scanning– CT scans– Container scans at airports
• Molecular changes in materials– Turns white topaz into blue topaz
![Page 18: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/18.jpg)
summary
• Charge– Alpha = positive– Beta = negative– Gamma = neutral
• Mass– Alpha = heavy– Beta = nearly massless– Gamma = massless
![Page 19: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/19.jpg)
Half life
• Describes the time required for nuclear material to be reduced by half
• Each radioactive isotope has different half lives– Carbon-11 = 20 minutes– Uranium-238 = 4.5 x 109 years
![Page 20: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/20.jpg)
Half life game
• Everyone tosses one coin
• Heads leave the game• Tails continue to toss
until no one is left in the game
• Questions– What does your graph
resemble?– Why is this?
![Page 21: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/21.jpg)
Predicting the quantity remainingNumber of elapsed half-lives
Fraction remaining Percentage remaining
0 1/1 100%
1 ½ 50%
2 ¼ 25%
3 1/8 12.5%
4 1/16 6.25%
n 1/2n 100% / 2n
![Page 22: Introduction to Radiation](https://reader035.vdocuments.site/reader035/viewer/2022062222/56816180550346895dd11089/html5/thumbnails/22.jpg)
Applications of half life
• Dating– Carbon-14 decays to carbon-12. The ratio can be
used to date archeological artifacts• Toxicology– Predict the effects of certain toxins in the human
body over time