Question

Chapter 35, Problem 035 we wish to coat flat glass (n = 1.50) with a transparent material (n = 1.32) so that reflection of light at wavelength 539 nm is eliminated by interference, what minimum thickness can the coating have to do this? Number the tolerance is +/-9% Units

Answer 1

for thin film interference... destructive interference with nvalues 1.00 > 1.32 > 1.50 we use

2 t n = $\lambda$ ( m +1/2)  

The minimum thickness is when m = 0 so

t = $\lambda$ (1/2) /2n = $\lambda$ / 4n = 539 nm / (4 *1.32) = 102.08 nm