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    2015 Q3 (Spectrometer experiment) acc98

    can someone PLEASE explain to me why in 2015 Q3 when calculating the wavelength of light in the marking scheme it says:

    when calculating d ( formula, d=1/n(lines per mm) ) it says to put d=1/80000, when in the question it says 'the diffraction grating had 80 lines per mm'

    should it not be 1/80??? as the formula is d=1/lines per mm.

    1. avatar image

      Midleton

      You have to change it to lines per metre

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      jameslindsaypc

      You multiply 80 by 1000 just like converting mm to m to get 80000

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      Kevin baker

      welll

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      Harish

      Change it to lines per metre. The SI unit of length is the metre

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      acc98

      thanks guys, i have it written in my textbook wrong for some reason

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      Me

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