Question

path difference formula in optics
​

Answer 1

Answer:

δ = (2π/λ)(OPD)

where π is a constant (3.14159265) and λ is the wavelength of light illuminating the specimen. The optical path difference is the product of two terms: the thickness (t) and the difference in refractive index (n). The OPD can often be quite large even though the thickness of the object is quite thin.