Physic Topic 2 - The Electromagnetic Spectrum

Beyond the Visible
1. Infra-red
  1. William Herschel (1738 - 1822) was a British Astronomer.
    1. He discovered Infra-red by using a prism to split the sunlight into a spectrum and then put a thermometers either side of the spectrum.
      1. As he changed the colour from violet to red, he found that the temperature rose.
        He wondered what would happen if he measured the temperature just beyond the red end on the spectrum, where there was no visible light.
        He found this gave him the highest temperature and he named it Infra-red, as it was just after the red end of the spectrum.
2. Ultra-violet
  1. Johann Ritter (1776 - 1810)
    1. He found out about Herschel's work and in 1801 set about trying to find 'invisible rays' at the other end of the spectrum.
      1. He used silver chloride, a chemical that breaks down to give a black colour when exposed to light.
        It was already known that silver chloride turned black more quickly in violet light that in red light.
        Ritter showed that silver chloride turned black fastest when exposed to 'invisible rays' just beyond violet.
        It was called Ultra-violet as it is just beyond violet on the spectrum.
The Electromagnetic Spectrum
1. Shortest Wavelenght - Highest Frequency
  1. Longest Wavelength - Lowest Frequency
    1. Radio waves
  2. Gamma rays
2. Gamma rays
  1. X-rays
    1. Ultra-violet rays
      1. Visible Light
        Infra-red
        Microwaves
        Radio waves
3. Good
  1. Xylophonest
    1. Use
      1. Very
        Interesting
        Musical
        Rhythms
4. Electromagnetic waves can travel without any particles to vibrate. This means that they can move easily through a vacuum, such as space.
  1. All electromagnetic waves travel at 300,000 kilometres per second in a vacuum.
Dangers and Uses
1. Gamma rays are used to kill cancer cells.
2. X-rays are used to take photographs of your body and to scan your luggage at airports.
  1. Exc
3. Sunlight contains ultra-violet light.
  1. Ultra-violet light can also damage our eyes, which can lead to cataracts.
  2. Excessive exposure to Gamma rays, X-rays and Ultra-violet rays may cause mutations, or changes in DNA that may kill cells or cause cancer.
4. Infra-red radiation is used in thermal imaging cameras, this means anything that emits heat can be seen in the dark or fog.
5. Ultra-violet is used in the making of bank notes, under UV light the fluorescent markings become visible to the human eye, proving if it is forged.
Ionising Radiation
1. Gamma
  1. Electromagnetic waves are emitted from the nucleus.
  2. It is a particle.
    1. It is high energy.
2. Alpha
  1. It is a particle.
    1. Helium is emitted from the nucleus.
3. Beta
  1. It is a particle.
    1. Electrons are emitted from a neutron (changing it to a proton).

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Physic Topic 2 - The Electromagnetic Spectrum

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