UV light

• what is visible light?

  the light we use to see, it appears as different colours depending on the wavelength
• red has the _______ wavelength while violet has the ________

  longest, shortest
• how can visible light be used with optic fibres for transmitting data really quickly over long distances?

  • encoding them with data
  • optic fibres are thin glass or plastic fibres that are able to transmit pulses of light over long distances.
  • this is because the light is reflected every time it hits the surface of the optic fibres. it ends up bouncing back and fourth for the entire journey.
  • until it reaches the end of the fibre where it can be interpreted
  • to make sure this works we must use materials that will totally reflect the light and make sure the the reflection is specular.
• what is the alternative to using optic fibres to transmit data really quickly?

  • using copper wires and electricity
• what is the advantage of using optic wires to transfer data really quickly?

  they can transmit much more information and the signals are less likely to be distorted during transmission
• how long is the wavelength of ultraviolet?

  shorter wavelength than visible light
• what is the most well known example of UV light?

  the UV light that is emitted from the sun
• how can we generate UV light ourselves?

  • sun beds
• what is fluorescence?


  a property of certain chemicals where ultraviolet light is absorbed and then the energy is reemitted as visible light. this is how fluorescent paints look so bright, because they are emitting light not only reflecting it.
• how do fluorescent lights work?

  • the lights generate UV radiation
  • all of the radiation is absorbed by a layer of phosphorus that is inside the glass bulb
  • because the phosphorus has so much energy, it reemits the energy as visible light
  • we have turned the ultraviolet light into visible light
• what is the benefit of using UV fluorescent bulbs?

  • they're really energy efficient
  • saving on electricity bills and CO2 emissions
• how is UV radiation used in security?

  • by using special security pens we can mark property and write codes that are completely invisible until we shine UV light on them
  • we also do this with passports and banknotes, this means they're harder to copy and its easier to detect fraud
• how is UV radiation used to sterilise water?

  • it destroys microorganisms