Caution
Fill in all input cells.
Choose all parameters unit.
z is algebraic. R1 and R2 are infinite (if they are plane) or algebraic. Enter "infinite" for a plane surface. Other input parameters are positive.
Positive direction is according to the sense of the horizontal arrow provided for this purpose..

n can be either a numeric value or the reference of a glass from the catalog. If a reference of a glass is selected, the calculation considers the refraction index of this glass at the wavelength lam defined in the current page.