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Why do energy saving bulbs look dim when first switched on? watch

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    Hi guys, i'm just struggling with this question and was hoping someone could help me. I'm also struggling to find any online sources relevant to this question.
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    In the past, some energy saving lightbulbs still had only tungsten filaments, but with incorporate special coatings on the glass envelope, which reduced transmission of infrared radiation. Such bulbs are usually dull when first switched on and gradually reach their maximum brightness over a short period of time. Explain this change of brightness with time by using the Stefan-Boltzmann Law and ‘Greenhouse effect’.
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    Any help would be greatly appreciated
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    Well the compact fluorescent (CFL) types...

    take a while to 'warm up'
    There's an electronic circuit in the base of the lamp that slowly increases the current over a minute or so after switch on - it prolongs the life of the electrodes at either end of the tube if they warm up slowly afaik.

    That's pretty much an obsolete technology now though 'cos you can get LED bulbs that are instant full brightness and more efficient in terms of light output per watt.
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    coz ur eyes cant take the brightness of the light at first
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    Oh didn't notice it was undergraduate level.

    I expect you'll have to say something about taking time for heat to ionise the mercury vapour... but afaik it's really about allowing the temperature to equalise gradually and therefore not cracking the glass around the conductors taking the current to the heater by differential thermal expansion.
 
 
 
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