X-rays are used        X-rays and gamma       Gamma rays                  Microwaves                       Infrared-IR
in ...
Alpha particle
                      A radioactive substance
 Marie Curie-                                                ...
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P1b revision SJT


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P1b revision SJT

  1. 1. X-rays are used X-rays and gamma Gamma rays Microwaves Infrared-IR in hospitals to rays damage living •Have the shortest •Short waves •All objects emit IR. The hotter take radiographs. tissue when they wavelengths •Can pass through the object the more IR it emits pass through it. • used to kill atmosphere for satellite •IR heat objects. bacteria in food, communications •Uses: heaters, IR scanners, IR Large doses can kill sterilise surgical •Used in cooking, microwave cameras, remote controls, optical cells, small doses equipment and kill ovens - heat water molecules fibres and communications can cause cancer cancer cells. X-rays and gamma rays are absorbed by dense material such as bone and metal but pass through soft tissue Radio waves Optical Fibres •Have the longest wavelengths •Visible light and IR carry •Used in communications signals •Radio waves - smallest long waves - •Carry more info than wires 300,000Hz+ •More secure, signal stays in •Carry radio, TV, mobile phone signals wire •Alternating voltage  ariel  receiver •Frequency of radio wave = alternating voltage of carrier wave •High frequency radio waves- •Carry more information Analogue signals vary •Have a shorter range continuously in amplitude or •Less diffraction frequency Digital signals are on or off. Radio waves are Digital signal free of reflected by the interference and carry more IONOSPHERE. information. P1b, Physics Carrier waves (radio, Stronger in microwaves etc) carries summer digital/analogue signal Ultraviolet-UV Found naturally in sunlight. UV harms the skin and The use of eyes, causes a sun tan, used radio waves All EM waves travel through space at speed of in security markers depends on light (300 million m/s). the frequency Wave speed= Frequency X Wavelength of the waves (m/s) (Hz) (m)
  2. 2. Alpha particle A radioactive substance Marie Curie- Positive charge, deflected in magnetic and contains unstable nuclei. Discovered electric fields, Helium nucleus An unstable nucleus Radioactivity. Beta particle becomes stable by Worked with Negative charge, deflected in magnetic emitting radiation. uranium. Died of and electric fields, electron emitted from cancer because nucleus of her work. Alpha Radiation- Stopped by paper or a Gamma particles few cm of air No charge, not deflected in magnetic and Beta Radiation– Stopped by thin aluminium electric fields, EM wave or about 1m of air Gamma radiation- Stopped by thick lead or concrete and has an unlimited range in air Uses of radioactivity •Automatic thickness monitoring- uses beta Half life •Radioactive tracers- uses gamma Unstable radioactive elements decay Time it takes for number of •Radioactive carbon/uranium dating randomly and give off particles radioactive nuclei of the isotope to •Carbon- wood Isotope atoms of an element have decay to half its initial value. •Uranium- rocks different numbers of neutrons •Smoke detectors- uses alpha Detect radiation with Geiger Muller Tube (GM tube) Big Bang (BB)Theory •Massive explosion from a Isotopes small point Different •Background microwave types of radiation is radiation atoms of created just after the BB. the same •Created as high energy chemical gamma radiation after BB element, The Earths atmosphere Ionisation- Alpha and beta particles As universe expanded, it each having absorbs all electromagnetic knock electrons out of atoms stretched into longer and a different waves, except visible light, longer wavelengths. number of radio waves and some UV neutrons P1b Physics radiation. Satellite detectors are used to make observations outside •Light from distant galaxy is red- the visible and radio spectrum. shifted to longer wavelengths Clear images are observed •Edwin Hubble discovered that light using telescopes on satellites from galaxies were red-shifted detecting visible light. •Distant galaxies are moving away from us •Space, time and matter created •Speed of distant galaxy is by the Big Bang The most distant galaxies are proportional to distance from us •BIG BANG happened 13,000 about 13 million light years away. The universe is expanding million years ago