Hello All, I am having some issues with calculating the measurement uncertainty when there is a mismatch in the index of refraction between a fluid and an interface. If am using an unobtrusive measurement technique such as Laser Doppler Velocimetry, how would I be able to quantify the uncertainty associated with a slight mismatch in the index of refraction, such as glass and water. From LDV, I can get a velocity measurement, but how would I be able to quantify the uncertainty in the velocity measurement given that there is some difference in the two mediums. Given that I know the two refractive indexes of the mediums and the thickness of the material, how can I calculate the uncertainty? If anyone has any references to this subject or hints, I would greatly appreciate it. Thanks!