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- 1. Prof.Dr.Tarek Elnimr L 3& L4 Presented to the Biology Departments in Faculty of Sciences on February 15 , 2009
- 2. Electromagnetic Waves vs. Particle Radiation <ul><li>Radiation </li></ul><ul><ul><li>Energy transfer through matter or space </li></ul></ul><ul><li>Classification of Radiation Energy </li></ul><ul><ul><li>Electromagnetic </li></ul></ul><ul><ul><ul><li>Made of electric and magnetic fields </li></ul></ul></ul><ul><ul><ul><li>Radio, UV, microwave, gamma rays, visible light, x-rays, and infra red (listed in order from lowest frequency) </li></ul></ul></ul>
- 3. Electromagnetic Radiation <ul><li>Interrelated electric and magnetic fields traveling through space </li></ul><ul><li>All electromagnetic radiation travels at c = 3 10 8 m/s in vacuum – the cosmic speed limit! </li></ul><ul><ul><li>real number is 299792458.0 m/s exactly </li></ul></ul>Spring 2008
- 4. Electromagnetic Spectrum <ul><li>Diagram of EM spectrum (w/ color) </li></ul>
- 5. Radioactivity: Gamma Rays The Electromagnetic Spectrum
- 6. Stratospheric Ozone and Ultraviolet Radiation (UVR) <ul><li>Ultra-violet radiation (UVR) high energy electromagnetic wave emitted from the sun. It is made up of wavelengths ranging from 100nm to 400nm. </li></ul><ul><li>UV radiation includes UV-A , the least dangerous form of UV radiation, with a wavelength range between 315nm to 400nm, UV-B with a wavelength range between 280nm to 315nm, and UV-C which is the most dangerous between 100nm to 280nm. UV-C is unable to reach Earth’s surface due to stratospheric ozone’s ability to absorb it. (Last, 2006) </li></ul>
- 7. for visible light is approximately 100 nm red 750 - 610 nm long - low purple 450 - 400 nm short - high
- 8. Light & the Electromagnetic Spectrum
- 9. Wavelength Units <ul><li>Meters </li></ul><ul><ul><li>More commonly in nanometers (1 nm = 10 -9 meters) </li></ul></ul><ul><li>Angstroms still used </li></ul><ul><ul><li>Named for Swedish Astronomer who first named these wavelengths </li></ul></ul><ul><ul><li>1 nanometer = 10 A o </li></ul></ul>
- 10. THE ENERGIES OF ELECTROMAGNETIC WAVES (nu-bar) represents wavenumber, the number of wavelengths in 1 cm
- 11. 4) Characteristics of Waves - wavelength - distance between consecutive peaks - crests - measured in m, nm, angstroms.
- 12. <ul><li>All life is dependent on small doses of electromagnetic radiation. </li></ul><ul><li>For example, photosynthesis and vision use the suns radiation. </li></ul>
- 13. Low High ENERGY Radio waves Microwaves Radar Infrared Visible light Ultra-violet X-ray Gamma-ray Non-ionizing radiation Ionizing radiation
- 14. Radiation is Energy <ul><li>The energy is given off by unstable (radioactive) atoms and some machines. </li></ul><ul><li>For this talk, we will be focusing on ionizing radiation and its health effects. </li></ul>
- 15. frequency - (nu) - number of times per second a crest passes a given point (cycles per second) 1 Hz = 1 cycle per second = 1/sec =sec -1 u = speed = X nm/wave X wave/sec = nm/sec for light - speed of electromagnetic radiation in a vacuum is a constant - c - 2.998 X 10 8 m/sec X = c for light
- 16. nu is inversely proportional to the wavelength. What does this mean? The range of frequencies or wave lengths is called the electromagnetic spectrum - it ranges from gamma rays to TV, FM, AM radio waves.
- 17. Forms of Radiation <ul><li>When unstable atoms transform, they often eject particles from their nucleus. The most common of these are: </li></ul><ul><ul><li>Alpha Radiation High energy, but short range (travels an inch in air, not an external hazard) </li></ul></ul><ul><ul><li>Beta Radiation Longer range (10 – 20 feet in air) and can be a skin and eye hazard for high activity beta sources. </li></ul></ul><ul><li>Gamma Rays (electromagnetic radiation) Often accompany particle radiation. This “penetrating” radiation is an external hazard and can travel 100s of feet in air. </li></ul>gamma gamma
- 18. Nonionizing Ultraviolet, visible, infrared, microwaves, radio & TV, power transmission Ionizing Radiation capable for producing ions when interacting with matter – x-rays, alpha, beta, gamma, cosmic rays
- 19. Nonionizing Ultraviolet, visible, infrared, microwaves, radio & TV, power transmission Ionizing Radiation capable for producing ions when interacting with matter – x-rays, alpha, beta, gamma, cosmic rays
- 20. <ul><li>Sources </li></ul><ul><ul><li>Ultraviolet light </li></ul></ul><ul><ul><li>Visible light </li></ul></ul><ul><ul><li>Infrared radiation </li></ul></ul><ul><ul><li>Microwaves </li></ul></ul><ul><ul><li>Radio & TV </li></ul></ul><ul><ul><li>Power transmission </li></ul></ul>
- 21. <ul><li>Ultraviolet – Black light – induce fluorescence in some materials </li></ul><ul><li>Vision – very small portion that animals use to process visual information </li></ul><ul><li>Heat – infrared – a little beyond the red spectrum </li></ul><ul><li>Radio waves – beyond infrared </li></ul><ul><li>Micro waves </li></ul><ul><li>Electrical power transmission – 60 cycles per second with a wave length of 1 to 2 million meters. </li></ul>
- 22. Ionizing Electromagnetic Radiation <ul><li>Ionizing Electromagnetic Radiations do have enough energy to remove electrons from atoms, such as: </li></ul><ul><ul><li>X-rays </li></ul></ul><ul><ul><li>Gamma rays </li></ul></ul><ul><ul><li>Neutrons </li></ul></ul><ul><ul><li>Alpha Particles </li></ul></ul>
- 23. Ionization Atom Electron Ionizing Radiation Ion More Reactive !! Biological Effect
- 24. <ul><li>The process by which a neutral atom acquires a positive or negative charge </li></ul>Ionization electron is stripped from atom - - - - The neutral atom gains a + charge = an ion + + Alpha Particle
- 25. <ul><li>Ionization </li></ul>Ionization by a Beta particle: - - - - The neutral absorber atom acquires a positive charge Beta Particle - Colliding Coulombic Fields ejected electron
- 26. Radiation and Radioactive Material are a Natural Part of Our Lives <ul><li>We are constantly exposed to low levels of radiation from outer space, earth, and the healing arts. </li></ul><ul><li>Low levels of naturally occurring radioactive material are in our environment, the food we eat, and in many consumer products. </li></ul><ul><li>Some consumer products also contain small amounts of man-made radioactive material. </li></ul>Smoke Detector
- 27. Non-Ionizing Electromagnetic Radiation <ul><li>Non-Ionizing Electromagnetic Radiations do not have enough energy to remove electrons from atoms, such as: </li></ul><ul><ul><li>Ultraviolet Radiation </li></ul></ul><ul><ul><li>Light </li></ul></ul><ul><ul><li>Infrared Radiation </li></ul></ul><ul><ul><li>Microwaves </li></ul></ul><ul><ul><li>Radio Waves </li></ul></ul>
- 29. Microwaves <ul><li>3 major uses in our society </li></ul><ul><ul><li>Cooking (Ovens) </li></ul></ul>
- 30. Microwaves <ul><li>3 major uses in our society </li></ul><ul><ul><li>Cell phones </li></ul></ul><ul><ul><li>Radar </li></ul></ul>
- 31. Infrared Radiation (Heat)
- 32. <ul><li>Energy between 750 nm to 0.3 cm </li></ul><ul><li>The energy of heat – Heat is the transfer of energy </li></ul><ul><li>Can damage – cornea, iris, retina and lens of the eye (glass workers – “glass blower’s cataract”) </li></ul>
- 33. <ul><li>Energy between 400 and 750 nm </li></ul><ul><li>High energy – bright light produces of number of adaptive responses </li></ul><ul><li>Standards are set for the intensity of light in the work place (measured in candles or lumens) </li></ul>
- 34. <ul><li>Sun light </li></ul><ul><li>Most harmful UV is absorbed by the atmosphere – depends on altitude </li></ul><ul><li>Fluorescent lamps </li></ul><ul><li>Electric arc welding </li></ul><ul><ul><li>Can damage the eye (cornea) </li></ul></ul><ul><li>Germicidal lamps </li></ul><ul><li>Eye damage from sun light </li></ul><ul><li>Skin cancer </li></ul>
- 35. <ul><li>High ultraviolet – kills bacterial and other infectious agents </li></ul><ul><li>High dose causes - sun burn – increased risk of skin cancer </li></ul><ul><li>Pigmentation that results in suntan </li></ul><ul><li>Suntan lotions contain chemicals that absorb UV radiation </li></ul><ul><li>Reaction in the skin to produce Vitamin D that prevents rickets </li></ul><ul><li>Strongly absorbed by air – thus the danger of hole in the atmosphere </li></ul>
- 36. Too much ultra-violet light can result in : <ul><li>Skin cancer </li></ul><ul><li>Eye damage such as cataracts </li></ul><ul><li>Immune system damage </li></ul><ul><li>Reduction in phytoplankton </li></ul><ul><li>Damage to the DNA in various life-forms </li></ul><ul><ul><li>this has been as observed in Antarctic ice-fish that lack pigments to shield them from the ultra-violet light (they've never needed them before) </li></ul></ul><ul><li>Possibly other things too that we don't know about at the moment </li></ul>
- 37. Ionization Defined Radiation capable for producing ions when interacting with matter – in other words enough energy to remove an electron from an atom. Sources – x-rays, radioactive material produce alpha, beta, and gamma radiation, cosmic rays from the sun and space.
- 38. Radioactive Material <ul><li>Either natural or created in nuclear reactor or accelerator </li></ul><ul><li>Radioactive material is unstable and emits energy in order to return to a more stable state (particles or gamma-rays) </li></ul><ul><li>Half-life – time for radioactive material to decay by one-half </li></ul>
- 39. Hazards of Radiation <ul><li>“ Radiation is radiation. It cannot be seen; it cannot be felt; it cannot be smelled; it cannot be heard; and it cannot be touched. Yet it exisits, and though its proper use has been immeasurable benefit to mankind, its abuse or improper use presents great hazards.” </li></ul>
- 40. <ul><li>The process by which a neutral atom acquires a positive or negative charge </li></ul>Ionization electron is stripped from atom - - - - The neutral atom gains a + charge = an ion + + Alpha Particle
- 42. Alpha Particles <ul><li>Two neutrons and two protons </li></ul><ul><li>Charge of +2 </li></ul><ul><li>Emitted from nucleus of radioactive atoms </li></ul><ul><li>Transfer energy in very short distances (10 cm in air) </li></ul><ul><li>Shielded by paper or layer of skin </li></ul><ul><li>Primary hazard from internal exposure </li></ul><ul><li>Alpha emitters can accumulate in tissue (bone, kidney, liver, lung, spleen) causing local damage </li></ul>
- 43. Radioactivity: Beta Rays
- 45. Beta Particles <ul><li>Small electrically charged particles similar to electrons </li></ul><ul><li>Charge of -1 </li></ul><ul><li>Ejected from nuclei of radioactive atoms </li></ul><ul><li>Emitted with various kinetic energies </li></ul><ul><li>Shielded by wood, body penetration 0.2 to 1.3 cm depending on energy </li></ul><ul><li>Can cause skin burns or be an internal hazard of ingested </li></ul>
- 47. Gamma-rays <ul><li>Electromagnetic photons or radiation (identical to x-rays except for source) </li></ul><ul><li>Emitted from nucleus of radioactive atoms – spontaneous emission </li></ul><ul><li>Emitted with kinetic energy related to radioactive source </li></ul><ul><li>Highly penetrating – extensive shielding required </li></ul><ul><li>Serious external radiation hazard </li></ul>
- 48. X-rays <ul><li>Overlap with gamma-rays </li></ul><ul><li>Electromagnetic photons or radiation </li></ul><ul><li>Produced from orbiting electrons or free electrons – usually machine produced </li></ul><ul><li>Produced when electrons strike a target material inside and x-ray tube </li></ul><ul><li>Emitted with various energies & wavelengths </li></ul><ul><li>Highly penetrating – extensive shielding required </li></ul><ul><li>External radiation hazard </li></ul><ul><li>Discovered in 1895 by Roentgen </li></ul>

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