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Thread: TEST Your laser safety IQ--

  1. #21
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    Back in June 2010 member DiRollin started a thread--at LPF


    prompted by the surge of newcomers wanting a Wicked Laser-

    There are a number of good links and a 10 question quiz- but afaik no 'key' so we will need to come up with the correct answers on our own.
    When I took it I added A. B. C. etc to the possible answers- I copied my answers--

    the test--

    Safety Quiz:
    http://www.coherent.com/downloads/Laser_Safety_Quiz.pdf

    anyhoo- one of the safety videos attached has every question mentioned and answered so plz - take the quiz THEN see the vids unless yer skeeared--
    but dont put the answers here--

    take the quiz- save your answers- see the vids and THEN take the quiz over etc.

    get all the links here:

    http://laserpointerforums.com/f53/ar...uiz-51864.html

    hak
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  2. #22
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    Hey Hak - Thanks for posting.

    I think I dropped 4 or 5 but it's great to have the impetus to test my knowledge and think about laser safety - despite being in the UK and having less stringent controls most of the questions relate to what we all do with our photons, wherever we are.

    Keith

  3. #23
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    your very welcome Keith--


    My motives are not entirely altruistic(?) as i failed my first go at the LSO exam - I wont make a lot of excuses- (my laptop lost wifi-& I had links to stuff that would have helped me to pass=maybe)=so i need to really be on top of my game for the do-over next month (and another $100 -ouch!)

    I do however want more at the pointer forum to be aware of safety and the consequences if not careful-- as IMHO 99.9% of the idiots who commit these crimes with thier lasers are NOT members here--nor ever will be.-

    -- if you go to laserpointersafety.com and see the 'sentences' handed out you will read some things they had to say about the 'experience' -- Once you are a convicted felon your entire world is rocked-- and never the same after...

    If anyone know of any math Qs for this or can make up a Q I would like to see that posted here.. for the LSO these are just extra credit- no loss if not answered or incorrect- I did not even try- too bad just getting one math Q right and i would very likely have passed.

    My laptop crashed BAD(all on my HD was gone) right after SELEM this year so I need to get all the stuff I lost and have it back where i can use it--



    hak
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  4. #24
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    b u m p

    a second quiz is linked in post #21 above- its from Coherant and was posted a long time ago.

    good luck
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  5. #25
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    BUMPING


    Been finding a mountain of Laser Safety Info on the webbz as every university has lasers & safe use is paramount. So all have a lot on laser safety-sample quizzes=math Qs etc.

    Found this question and not 100% sure what is the correct answer==

    It was about laser induced biological skin exposure= "which is NOT a 'item of concern' " -I choose 'divergence' by process of elimination--

    was I correct??

    the other choices were-
    -size of area exposed-
    -beam penetration-
    -exposure limits

    they do not give the answers to that quiz--


    thanks hak
    Last edited by hakzaw1; 11-22-2014 at 17:18.
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  6. #26
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    I would have said size of area exposed.

    I would have said Divergence is a concern because the lower the divergence the higher the power density and thus potential for damage, the deeper the penetration the greater the cell damage and exposure limits are obviously a concern if you're trying to avoid exposing people to potentially harmful beams, which just leaves the size of the are exposed.

  7. #27
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    IIRC on-line I read that the size (area) exposed on skin is a factor of concern.

    I will find it-brb

    meantime

    check this out--
    typo maybe??
    U.of Chicago

    here-- http://safety.uchicago.edu/pp/laser/mpe_nhz.shtml
    "The Maximum Permissible Exposure (MPE)
    The single most useful number in laser safety calculations is the Maximum Permissible Exposure (MPE). This is the minimum irradiance or radiant exposure that may be incident upon the eye (or the skin) without causing biological damage."

    "MINIMUM???? dont they mean max.????
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  8. #28
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    Click image for larger version. 

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ID:	45494WARNING GRAPHIC IMAGES

    http://www2.lbl.gov/ehs/safety/lasers/bioeffects.shtml

    from the above

    '

    "Skin penetration by laser type

    There is quite a variation in depth of penetration over the range of wavelengths, with the maximum occurring around 700 to 1200 nm. Injury thresholds resulting from exposure of less than 10 seconds to the skin from far-infrared and far-ultraviolet radiation are superficial and may involve changes to the outer dead layer of the skin. A temporary skin injury may be painful if sufficiently severe, but it will eventually heal, often without any sign of injury. Burns to larger areas of the skin are more serious, as they may lead to serious loss of body fluids. Hazardous exposure of large areas of the skin is unlikely to be encountered in normal laser work." end quote (Berkely)
    so afaik that eliminates
    1) beam penetration
    and
    3) size of exposed area
    _______________________
    2)Exposure limits
    4) beam divergence
    not sure which is correct (not a factor of concern)
    My thinking , considering the quick spread of IR, for example makes it less dangerous at distance so..

    not sure what limits they mean=

    FYI the pic of the finger with hole--went out thru fingernail= look close and you can see he moved it & the burn line to the hole.
    Last edited by hakzaw1; 11-25-2014 at 19:57.
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  9. #29
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    update bump

    Concerning your question, the answers are a bit odd - Divergence does not directly come into play for skin exposures, except as it may affect spot size on the skin surface. Similarly, the exposed area is does not directly affect matters, except again as a function of irradiance. A larger area burn would have a more serious effect, but this would also necessitate more laser power.

    I think I would have written this a bit differently, with answers as Wavelength (which has a decided effect), pulse duration (pulses tend to cause more disruption of tissue), blood flow (as this acts as the cooling mechanism), and as a non-effect, maybe coherence...


    ^^^^ ^
    the reply from Greg Makov-instructor for ILDA LSO..

    I read that if the area exposed is large -there is more possible damage due to loss of fluids in the exposed areas--kinda like getting a sunburn only on your neck as opposed to getting sunburn over a very large area==much worse..==and regardless of the divergence is a set size as it hits skin- and the beam size would not change much as all as it goes deeper into the skin.

    *************************

    True or false

    The Maximum Permissible Exposure (MPE)
    The single most useful number in laser safety calculations is the Maximum Permissible Exposure (MPE). This is the minimum irradiance or radiant exposure that may be incident upon the eye (or the skin) without causing biological damage.
    Last edited by hakzaw1; 11-27-2014 at 12:33.
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  10. #30
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    Even tho this is copypasta unchanged- typo??? minimum needs to be changed to maximum.

    University of Chicago-- has this in their site --must be embarrassing.
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