Answer:
t = 1.16 x 10⁻⁷ m = 116nm
Explanation:
Use the condition for destructive interference to find the thickness.
2nt = (m + 0.5) λ, where t is the thickness of the film, n is the refractive index of the film, m is an integer (which will be considered ‘0’ as there is no phase shift because the wave goes from a low index of refraction to a high index of refraction twice, that is, air to film and then film to glass ) and λ is the wavelength of light after going through the film.
t = (m + 0.5) x λ/2n
t = (0.5) x (640 x 10⁻⁹)/2 x 1.38
t = 1.16 x 10⁻⁷ m = 116nm
The thinnest film coating should be 116 nm for the destructive interference of the red light to take place.
Answer:
115.94 nm ≅ 116 nm
Explanation:
so,
2nt = (m+0.5) λ
t = [tex]\frac{m+0.5}{2n}[/tex] ₓ λ
t =(m+0.5)ₓ[tex]\frac{(640nm)}{2*1.38}[/tex]
For minimum value of "t" ,"m" should be 0
t = [tex]\frac{0.5*640nm}{2*1.38}[/tex]
t = 115.94≅ 116nm
