[header] How to calculate the refractive index in physics [title] Measure the width of the transparent object. [step] For example, a pane of window glass has a thickness that may be stated by the manufacturer, but which should be measured to ensure accurate calculation of the refractive index. [title] Send light from a point light source through the object. 
[step] Monochromatic point light sources are available through laboratory supply outlets. Place the point light source a known distance from the surface of the object.