Waves and Radiation

Types of waves
1. Transverse
  1. The energy of a transverse wave travels at a right angle tot he direction it is traveling in. It doesn't need particles to move. An example of a transverse wave is a water wave
2. Longitudinal
  1. The energy of a longitudinal wave travels in the same direction that it is traveling in. It needs particles to move. An example of a longitudinal wave is sound.
Speed
1. Sound
  1. 340 m/s (in air)
2. Light
  1. 300,000,000 m/s (in air / vacume)
  2. 200,000,000 m/s (in an Optical fiber)
3. electromagnetic spectrum
  1. 300,000,000 m/s (through a vacume)
Wave
1. Frequency
  1. Frequency is defined as the number of waves per second
  2. Frequency is measured in Hertz (Hz)
2. Period
  1. Period Is the number of waves to pass (a certain point)
Angles
1. Reflection
  1. Angle of incident = Angle of reflection
2. Refraction
  1. When a ray of light Travels from thinner material (air) to a more dense material (glass), the ray of light will refract (bend) towards the normal.
  2. The angle of incidence is greater then the angle of refraction
3. Total internal reflection
  1. At a certain angle (critical angle) the light doesn't refract out. It is trapped inside (total internal reflection). This is what occurs in optical fibers.
    1. optical fibers
      1. How light travels through an optical fiber
lenses
1. Convex (Converging)
  1. used to correct long sight
2. Concave (diverging)
  1. Used to correct short sight
3. power
  1. Have a negative focal length and power
  2. Have a positive focal length and power
Radiation
1. Backgrond
  1. The air around us is slightly radioactive - we are exposed to this background radiation 24 hours a day.
  2. Sources of background Radiation includes :
    1. Cosmic rays from outer space
    2. Rocks such as granite
    3. hospital waste from cancer treatment
    4. nuclear weapons tests
    5. leaks from nuclear power stations
2. Radioactive decay
  1. Radioactivity is the decay of ionising radiation
  2. The three main types of radiation are Alpha, Beta and Gamma
3. How to tell radioactive sources apart
  1. Alpha
    1. Alpha source can be reconised because it can not travel through papper
  2. Beta
    1. Beta source can be recognised because it can travel through paper but it can not travel through aluinium
  3. Gamma
    1. Gamma source can be reconised because it can travel through paper, aluminium and lead but lead has the biggest effect on gamma rays.
4. safety
  1. Don't touch with your hands use tongs
  2. Spend a limited amount of time around the source
  3. Don't stand in line with the source
  4. Don't point the source at anybody
  5. Kept in a lead line box
5. Ionisation of Atoms
  1. Radioactivity can knock electrons out of atoms. this is known as ionisation.
  2. Radioactivity Can ionise atoms in the cells of the human body - This can kill the cells or change their nature - The cell might grow in a different way to what they should or might change into cancer cells.
    1. Because radioactivity kills living cells, it is used to sterilise surgical instrument - the bacteria cells are killed
6. Activity
  1. Activity is the number of decays per second
7. Half life
  1. The half life is the time taken for the activity of a sample to drop by half
Electromagnetic spectrum
1. Visable light
  1. Violet refracts the most
  2. Red refracts the least
  3. Primary colours
    1. Red
    2. Blue
    3. Green
  4. Secondary colours
    1. yellow
    2. Magenta
    3. Cyan
modulation
1. Amplitude (AM)
  1. To transmit sound by radio a high frequency carrier wave is added to the sound (audio) signal.
  2. This can make the amplitude of the carrier wave change. (it has the same frequency but varying amplitude)
2. Frequency (FM)
  1. In this case the amplitude of the carrier wave stays the same but the sound signal it carries now varies the frequency

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Waves and Radiation

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	Created by Jodie Stewart over 10 years ago