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USEFUL FORMULAE IN MICROSCOPY

Objective Numerical Aperture (where n = refractive index, u = half objective acceptance angle)  NA = n(sinu)
Resolution - brighfield (where λ = wavelength - 0.55Ám standard, NAo = objective NA, NAc = condenser NA )

Resolution - darkfield (where λ = wavelength - 0.55Ám standard, NAo  = objective NA, NAc = condenser NA  )

Single lens magnification (where f = focal length in mm)

Objective magnification - finite tube length (where OTL = optical tube length, fo - objective focal length)

Objective magnification - infinity corrected (where f = focal length of standard infinity tube lens, fo = objective focal length) NB Standard infinty tube lens focal lengths are Leica & Nikon = 200mm, Olympus = 180mm, Zeiss = 160mm

Eyepiece magnification (where fe = focal length of eyepiece in mm)

Microscope magnification Mag = objective magnification x eyepiece magnification
Maximum useful visual magnification Magmax = 1000 x NA
Depth of focus (consider wavelength λ = 0.55)

Visual field of view (where FN = eyepiece field of view number, Magobj = objective magnification)

Image intensity (for epi-fluorescence substitute (NA)4   )