A thin film of oil with a refractive index of no = 1.25 is located on a smooth, wet pavement with a refractive index of nw = 1.41. When viewed from directly above, the film appears to be red with a wavelength of λ = 640 nm.
i. What is the correct equation for thin film interference for this situation?
ii. Based on that equation, what is the minimum thickness the film can be?
A piezoelectric stage converts voltage into small mechanical displacements. The exact relationship (voltage-displacement) is unknown, so a Michelson interferometer (with a HeNe laser, λ = 632 nm) is used to calibrate the stage and determine the relation between voltage and displacement. A mirror is connected to the stage and is used as one arm of the interferometer. The voltage on the stage is varied linearly from 0V to 10V. During this time, 50 bright fringes are counted.
i. How far did the stage move?
ii. What is the approximate relationship between the displacement (x) and the voltage (V)?
iii. If V = 2V, what is x?
During the fabrication of a small device, two slits are made in the device. To verify the fabrication process, a researcher wants to measure the distance between the centers of the two slits. She has a laser with a wavelength of λ = 1550 nm, and a screen is placed 1 m away. The laser is set to pass through the slits and onto the screen. On the screen, several bright fringes are seen, each 10 mm apart.
What is the spacing, d, of the slits?
