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1) You\'re investigating an oil spill for your state environmental protection ag

ID: 1303602 • Letter: 1

Question

1) You're investigating an oil spill for your state environmental protection agency. There's a thin film of oil on water, and you know its refractive index is 1.32. You shine white light vertically on the oil, and use a spectrometer to determine that the most strongly reflected wavelength is 505 nm.

Assuming first-order thin-film interference, what do you report for the thickness of the oil slick?

2)X-ray diffraction in potassium chloride (KCl) results in a first-order maximum when the X rays graze the crystal plane at 8.5 degrees.

If the x-ray wavelength is 97 pm, what is the spacing between crystal planes?

Explanation / Answer

1. 2 * 1.32 * d = 0.5 * 505*10^-9

d = 9.6*10^-8 = Answer

2. 2 * d * sin(theta) = m * wavelength

d = wavelength / (2 * sin(8.5 degrees)) = 328pm = Answer