Question

A thin film of polystyrene is used as an antireflective coating for fabulite (known as the substrate). The index of refraction of the polystyrene is 1.49, and the index of refraction of the fabulite is 2.409. (Figure 1) 

Part A 

What is the minimum thickness of film required? Assume that the wavelength of the light in air is 470 nanometers. 

Express your answer in nanometers.  

Answer 1

plz rate

Answer 2

The thickness of the film required is,

$$ \begin{aligned} d &=\frac{\lambda}{4 n} \\ &=\frac{470 \mathrm{~nm}}{4(1.49)} \\ &=\frac{470 \mathrm{~nm}}{5.96} \\ &=78.85 \mathrm{~nm} \end{aligned} $$