Question

You are working for a craft store in the manufacturing department. The craft store does an excellent business selling frames for artwork, along with accessories. One of the accessories is nonglare glass. When looking at artwork that is mounted behind normal glass, harsh reflections of the light source illuminating the artwork from the front are reflected into the eye of the observer, often obscuring a view of portions of the artwork. Nonglare glass has a thin film on the outside surface that provides destructive interference for light near the center of the visible spectrum. As a result, there is less reflection to obscure your view. Your department has been selling nonglare glass with the minimum possible thickness to create destructive interference for light of wavelength 510 nm. But the store has been receiving complaints that the very thin film is damaged when the glass is rubbed with a cloth and glass cleaner. As a result, your supervisor asks you to determine the next possible thickness of the film (in nm) that will provide the proper destructive interference. The index of refraction of the glass is 1.63 and the index of refraction of the film material is 1.43.

Answer 1

Step-by-step explanation:

For destructive interference in thin films , the condition is

2μ t =( 2n+1)λ/2

where μ is refractive index of thin layer , t is thickness of layer and λ is wave length of light used. In this case for second order thickness n = 1

μ = 1.43 and λ = 510 nm

2μ t = ( 2n+1)λ/2

t =( 2n+1)λ/4μ

= 3 x 510 nm / 4x 1.43

= 267.48 nm