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Homework Statement
A Michelson interferometer is illuminated with a laser with a wavelength of 514.5nm. A Haidinger fringe pattern is photographed with a lens of focal length 55mm. The diameter of the two adjacent circular fringes in the image are 1.53mm and 2.62mm.
How far would the mirror that is further away from the beamsplitter need to be moved in order to set the interferometer at zero path difference?
Homework Equations
Haidinger Fringe rp
rp=f*√[(p*λ)/d]
where
rp = Haidinger Fringe
f = focal length
p = order of interference
λ = wavelength
d = difference in distance between the two mirrors and beamsplitter
Effective path difference
2d*cosθ = pλ
The Attempt at a Solution
Trying to derive an equation for the two path differences from the Haidinger Fringe equation, which is independent of the p value, but I'm struggling...
rp=f*√[(p*λ)/d]
( rp / f )2 = (p*λ)/d
( rp / f )2 = 2d*cosθ/d
d = 2d*cosθ / ( rp / f )2
d = 2d*cos1.3644 / 1.31 mm/55mm
d = 2*cos1.3644 / 0.02381818181
d = 17.2082026858
2 * 17.2082026858 * cos1.3644 = pλ
p = 2 * 17.2082026858 * cos1.3644 / 5.145*10^-7
p = 7.05309334257 / 5.145*10^-7
p = 13708636.2344
5.145*10^-7 * 13708636.2344 = 7.05309334257 metres = difference in distance between the two mirrors and the beam splitter
So would the mirror need to be moved 7.05309334257 metres in order to set the interferometer at zero path difference?