1.9 UV Light Flashcards
What is visible light?
The light we use to see, different colour depending on the wavelength.
How can visible light be used for communication?
Optical fibres: thin glass or plastic fibres that are able to transmit pulses of light over long distances as the light is reflected every time it hits the surface and so ends up bouncing back and forth over the whole journey until it emerges out the end of the fibre where it can be interpreted.
How can optical fibres be used to benefit communication?
They can transmit data very quickly
What is important about the material used in optical fibres?
They must be materials that will totally reflect the light, not absorb, and also ensure that the reflection is specular rather than diffuse so the light isn’t scattered.
What is an alternative to optical fibres for communication?
Copper wires and electricity
Why are optical fibres better than copper wires for communication? (2)
- They can transmit much more information.
- The signals are less likely to be distorted during transmission.
How is fluorescence created?
Ultraviolet (UV) radiation is absorbed and then visible light is emitted.
How do fluorescent lights work?
They generate UV radiation and all of that radiation is absorbed by a layer of phosphorus that coats the inside of the glass bulb. Then, because the phosphorus has so much energy, it remits the energy as visible light.
What is the benefit to fluorescent lights?
They’re energy efficient so we can save on energy bills and carbon dioxide emissions, and they’re good to use when light is needed for long periods.
How is UV light used in security?
Security pens are used to mark property. UV light causes the ink to fluoresce (emit visible light), but the ink remains invisible in visible light.
How is UV light used in tanning salons?
UV lamps are used in tanning salons to give people an artificial suntan. Skin produces a brown pigment melanin in response to UV radiation - melanin absorbs UV radiation and protects the cells from damage.
How is UV light used to sterilise water?
It destroys microorganisms.
