Answer:
Thickness is 217 nm
Explanation:
For a thin film, constructive and destructive interference each has its own effects. Here constructive interference causes the light to be strongly reflected. The thickness can be determined from
[tex]2\times t\times n \times sin\theta=m\lambda[/tex]
here n is refractive index 1.38, m=1 , [tex]\theta[/tex]=0, [tex]\lambda[/tex]=600 nm
[tex]t=\frac{600 \times 10^{-9}}{2\times 1.38} \\t=217 nm[/tex]
