4. -1 points SerPSE9 37.P031.WI A thin film of oil (n 1.300 is located on smooth

Question

4. -1 points SerPSE9 37.P031.WI A thin film of oil (n 1.300 is located on smooth, wet pavement. When viewed perpendicular to the pavement, the film reflects most strongly red light at 640 nm and reflects no green light at 512 nm. How thick is the oil film? Need Help? Read t Watch It 5. C+ -5 points SerPSE9 37.P037.MI-SA. This question has several parts that must be completed sequentially. If you skip a part of the question, you will not receive any points for the skipped part, and you will not be able to come back to the skipped part. Tutorial Exercise An air wedge is formed between two glass plates separated at one edge by a very fine wire of circular cross section as shown in the figure below. When the wedge is illuminated from above by 505 ight and viewed from above, 28 dark fringes are observed. Calculate the diameter d of the wire. Click here to begin! Need Help? Read It

Explanation / Answer

Here ,

let the thickness of film is d nm

n = 1.30

wavelength of red = 640 nm

wavelength of green = 512 nm

for strong reflection

2 * n * d = m * 512

2 * 1.30 * d = 512*m

d = 196.9 * m nm

for zero reflection

2 * n * d = (m - 0.5) * 640

2 * 1.30 * d = (m - 0.5) * 640

d = (m - 0.5)* 246

for both to be same

196.9 * m = (m - 0.5)* 246

solving

m = 2.5 * 2

hence , thickness = 2.5 * 2 * 196.9

thickness = 984.5 nm

the thickness of film is 984.5 nm

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