:!!) My problem is that I am required to derive such formulae, which are: MEASUREMENT of the LASER wavelength. (1) 1 or lamda = 2* dm/m & (2) m=(n-1) ( 2*d/1)*(Dp/ Patm) dm= distance of the movable mirror moved toward a beam splitter. m= no. of fringes that cross a given reference point. Dp = Pressure(final)- Pressure(initial) d= distance of the vacuum air cell that was used upon experiment to generate fringes Patm= atmospheric pressure=760atm. I would appreciate any help deriving these formulae in step by step way.