Question

An interference filter is to be constructed for the isolation of the absorption wavelength for an organic compound. The dielectric material has refractive index of 1.34. If the thickness of the filter is 2.50 mu m what is the wavelength (in nm) of the first order interference that will be observed?

Answer 1

Given that ;

Wave length ; λ = 2.50 μm or 2.50 *10 ^-6 m

Because 1 μm = 10 ^-6 m

Refractive index , n = 1.34

If path difference is equal wave length , then first order interference is occurred.

Assume that the thickness of the layer be t

Path difference = n x t

According to the above statement n x t = λ

∴ t = λ / n

      = ( 2.50 x 10 ^-6 m) / 1.34

      = 1.87 x 10 ^-6 m

      = 1.87 μm