Two glass plates are arranged as in the following figure so that light reflected

Question

Two glass plates are arranged as in the following figure so that light reflected from the bottom surface of the top plate interferes with light reflected from top surface of the bottom plate. As one moves along the x-axis, the total reflected intensity alternates between bright and dark fringes. If there are a total of 24bright fringes across the entire width of the plates, what is the plate spacing d at the right edge? Assume the source of illumination is blue light with a wavelength of 410 nm.
µm

Explanation / Answer

The first reflection is not phase-reversed and the 2nd is. So each bright fringe is at a point where the two-way air trip 2d adds a path length of lambda/2 * an odd integer so the total phase difference including reflections is lambda * an integer. At the 24st fringe 2d = lambda/2*41 (the 24st odd integer).
2d = 48*410/2 nm
d = 4920nm =4.92 µm

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.