An experimenter uses a pair of flat plates and a monochromatic light source to m

Question

An experimenter uses a pair of flat plates and a monochromatic light source to measure the thickness of a strand of hair, similar to what was done in Part 4 of the lab. The situation is shown below (not to scale).

If the plates are 2 inches square (exactly), and the hair is between the two plates at one edge (as shown), the experimenter measures 14 fringes within a distance of 10 mm. The light source has a wavelength of 580 nm. What is the diameter of the strand of hair? (Units required.)

Hair Diameter: _______

Explanation / Answer

2 inches = 50.8 mm

fringe separation = 10/13 = 0.769mm

For every 0.769 mm to the side ( the fringe separation ) the plates must get half a wavelength further apart ( so that the path difference increases by a full wavelength )

There are 50.8/0.769 = 66.0598 fringes in the full 2 inches

daiameter of hair = 66.059*580*10^-9/2 = 0.00001915711 m

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