A beam of light with wavelength 559 nm in air hits a thin piece of glass 24.19 microns thick (with refractive index 1.667) at an angle of 17.2 degrees to the normal. What is the path difference between the two reflections from the layers of the glass, in wavelengths? [Note to get the phase shift we multiply this number by 2n, but this is modulo 2n, i.e. any integer number of wavelengths are 2n phase shifts, equivalent to no phase shift... basically in terms of phase we only really need the non-integer part of your answer. Note also that for the phase shift we would need to add a n for the reflection off the glass-air interface.]

A beam of light with wavelength 559 nm in air hits a thin piece of glass 24.19 microns thick (with refractive index 1.667) at an angle of 17.2 degrees to the normal. What is the path difference between the two reflections from the layers of the glass, in wavelengths? [Note to get the phase shift we multiply this number by 2n, but this is modulo 2n, i.e. any integer number of wavelengths are 2n phase shifts, equivalent to no phase shift... basically in terms of phase we only really need the non-integer part of your answer. Note also that for the phase shift we would need to add a n for the reflection off the glass-air interface.]