Visible light and UV radiation

• How does visible light appear different colors?

  It depends on the wavelength
• What is the order of colors in visible light?

  Red, orange, yellow, green, blue, indigo, violet
• How is visible light used for communication?

  Through optical fibers transmitting light pulses
• What are optical fibers made of?

  Thin glass or plastic fibers
• How does light travel through optical fibers?

  It reflects and bounces back and forth
• What is required for effective light transmission in optical fibers?

  Materials that totally reflect light
• What is the advantage of using optical fibers over copper wires?

  They transmit more information with less distortion
• Where does ultraviolet radiation fall on the spectrum?

  After visible light
• What is a common source of ultraviolet radiation?

  The Sun
• What is fluorescence?

  Ultraviolet light energy being absorbed and re-emitted as visible light
• Why do fluorescent paints appear bright?

  They emit visible light after absorbing UV light
• How do fluorescent lights work?

  They generate UV radiation absorbed by a layer of phosphorous, the phosphorus then re-emits the energy as visible light
• What is the benefit of using fluorescent bulbs?

  They are energy efficient (meaning that we save money on electricity bills and carbon dioxide emissions)
• How can UV radiation be used for security?

  By marking property with invisible codes, using a security pen
• What is one application of UV radiation in detecting forgeries?

  Used in passports and banknotes
• How does UV radiation sterilize water?

  It destroys microorganisms
• What are 3 the main uses of ultraviolet light?

  • Fluorescence in paints and lights
  • Security marking with UV pens
  • Sterilization of water
• What is visible light used for?

  Communication, using optical fibres
• Describe how visible light is used for communication using optical fibres.

  • A pulse of light is emitted through an optical fibre
  • The light bounces back and forth until it emerges at the other end of the fibre, where it can be interpreted
  • (The light is able to travel long distances because it is reflected every time it hits the surface)