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.

Midleton
You have to change it to lines per metre

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

Kevin baker
welll

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

acc98
thanks guys, i have it written in my textbook wrong for some reason

Me
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