If the wedge between the glass plates of Example 24-10 is filled with some transparent substance other than air- say, water-the pattern shifts because the wavelength of the light changes. In a material where the index of refraction is n, the wavelength is λn = λ/n where is the wavelength in vacuum (Eq. 24-1). How many dark bands would there be if the wedge of Example 24-10 were filled with water?