1-- Waves and radiation

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  • Created by: umar2312
  • Created on: 24-04-17 21:26
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  • Waves and Radiation
    • Waves
      • Longitudinal Wave
        • A longitudinal wave is a wave in which the vibration is along the same line as the direction of travel.
      • Transverse Waves
        • A transverse wave is one in which the vibration is at 90 degrees to the direction of travel.
      • The frequency of a wave is the number of waves that pass  a point in 1 second.
      • The wavelength is the horizontal distance between two adjacent troughs or peaks on the waves
      • The amplitude of a wave is half the vertical distance between a trough and a crest
      • A period of a wave is the time it takes for one wave to pass a point.
      • Reflection is when a wave changes direction by boucing off a surface.
      • Refraction occurs when a wave passes from one medium to another with a change in wave speed.
      • Diffraction is the bending on the wavefront as it encounters a barrier or gap. the degree of bending depends on the size of the barrier, or gap compared to the wavelength
      • interferenece occurs when two or more waves passing through the same region combine to form a resultant waveform.
      • Light
        • Since light is a wave it tavels in a straight line it can be reflected and refracted.
        • Light is a transverse wave that doesn't require a medium to travel through..
        • The law of reversibility states that a ray of light which tavels along any particular path it travel the same way back if reversed.
        • A convex lens is an oval shape and causes rays of light to converge to a focal point
        • A Concave length is the opposite shape and causes the rays of light to diverge.
        • When light speeds up as it passes from one medium to another the direction of the ray bends away from the normal. at a certain angle of incidence he refracted wave has an angle refraction of 90 degrees
    • Radiation
      • Types of Nuclear Radiation
        • Alpha Particles
          • Beta Particles
            • Gamma Rays
              • These are caused by the energy changes in nuclei. Often gamma rays are sent out the same time as alpha and beta
                • Gamma Rays have no mass or charge and carry energy from the nucleus leaving the nucleus in a more stable state
                  • Low ionising ability
                    • Absorbed by a thick piece of lead
            • These are fast moving electrons
              • They are special types of electrons as they come from the nucleus
                • Medium ionising ability
                  • Absorbed by aluminium
          • These are the nucei of helium atoms.
            • They have 2 Neutrons and 2 Protons in the nucleus and  therefore poaitively charged.
              • High ionising ability
                • Absorbed by skin, or a sheet of thin paper
      • ionisation is the adition or removal of an(some) electron(s) is called ionisation.
      • There are some atoms which have unstable nuclei which throw out particles, or energy, to make nucleus more stable.these atoms are called radioactive.
        • Radiation can be used in the treatment of cancer. The radioactive source cobalt-60 kills malignant cancer cells .
      • Electromagnetic Spectrum
        • In order of decreaasing wavelength, and increasing frequency and energy.
          • Radio Waves
            • Micro Waves
              • Infared Waves
                • Visible Light
                  • Ultra Violet
                    • X-Rays
                      • Gamma Rays
                    • The higher the frequency the more dangerous it is
                      • Gamma Rays
      • The activity of a radioactive source is the number of decays per second. (Bq)
      • Tha absorbed dose is the energy absorbed per unit mass
      • Background radiation comes from natural sources. EG Rocks, Cosmic rays, Building material, the human body.
      • The biological effects of radiation
        • All ionisng radiation can cause damage to the body. There is no minimum amount of radiation which is safe.The risk of biological harmfrom an exposure to radiation depends on :
          • The absorbed dose
          • The kind of radiation
          • The body organs or tissue exposed
      • Nuclear Fission occurs when a massive  unstable atomic nucleus splits into two nuclei , giving off energy and radiation
        • Nuclear Fusion occurs when two atomic nuclei fuse together to form a single, large nucleus. energy is released.

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