Answer:
t = 100 nm
Explanation:
given,
Refractive index of coating is n ' = 1.25
refractive index of glass is n = 1.5
assuming wavelength of the film = 500 nm
destructive interference is
[tex]m +\dfrac{1}{2}\times \lambda = 2 n't [/tex]
[tex]t = \dfrac{m +\dfrac{1}{2}\times \lambda }{2 n'}[/tex]
for minimum thickness m = 0
[tex]t = \dfrac{0+\dfrac{1}{2}\times \lambda}{2 n'}[/tex]
[tex]t = \dfrac{500}{4 n'}[/tex]
[tex]t = \dfrac{500}{4\times 1.25}[/tex]
t = 100 nm
hence, the minimum thickness required is t = 100 nm
