The lead architect on the design team of a new skyscraper decides that the outer

Question

The lead architect on the design team of a new skyscraper decides that the outer surface of the building’s windows need to be coated with a reflective layer in order to lower airconditioning costs. MgF2 is chosen for the reflective layer, which has a refractive index n=1.38. Assume that the refractive index of the window glass is 1.5 and that the reflective coating should work optimally at the peak of the sunlight spectrum, 500 nm.

A)What is the minimum thickness of film that is needed?

B)Suppose the layer needs to be thicker than 200 nm in order to hold up to the weather. What other thicknesses would also work? Give only the three thinnest ones

Explanation / Answer

A)
the minimum tickness for reflecting surface,

2*t = lamda/n

t = lamda/(2*n)

= 500 nm/(2*1.38)

= 181.1 nm <<<<<<-----------Answer

B) 181.nm is not possible.

so, next possibilites, t2 = 2*t1

= 2*181.1

= 362.2 nm <<<<<<-----------Answer

t3 = 3*t1

= 3*181.1

= 543.3 nm <<<<<<-----------Answer

t4 = 4*t1

= 4*181.1

= 724.4 nm <<<<<<-----------Answer

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