Reflection by thin layers. In the figure, light is incident perpendicularly on a

Question

Reflection by thin layers. In the figure, light is incident perpendicularly on a thin layer of material 2 that lies between (thicker) materials 1 and 3. (The rays are tilted only for clarity.) The waves of rays r_1 and r_2 interfere, and here we consider the type of interference to be either maximum (max) or minimum (min). The table below provides the indexes of refraction n_1, n_2, and n_3, the type of interference, and the wavelength lambda in nanometers of the light as measured in air. Give the third least thickness L.

Explanation / Answer

use the below condition to find the thickness.

        2nt = (m + .5)(lambda)

here, m = 0, 1, 2, ...

For the third least thickness, m = 2,

thus, the above equation becomes as follows:

2(1.64)(t) = (2.5)(630 nm)

              t = 480.18 nm = 480 nm

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