Light wave incident on and passing through a thin soap film

[tffnyyy]

here is the problem. i got 0.5 from the fact that thickness = (m)(lambda)/(2nf)

other equation for thickness is thickness = (m+1/2)(lambda)/(2nf)

 

[andrevdh]

It seems that you have value for the wavelength and or refractive index? Note also that they want the answer to two significant digits where you only supplied one. What are the units of d? Is it multiples of lambda? I notice that there is a lambda to the right of the answer?