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 $\lambda_n = \lambda/n$, where $\lambda$ 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?