- #1

kankerfist

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## Homework Statement

A point source of light (λ = 589 nm) is placed 0.4 mm above the surface of a glass mirror. Interference fringes are observed on a screen 6m away, and the interference is coming from light reflecting off the mirror and light coming directly from the source. Find the spacing of the fringes

## Homework Equations

reflection from the mirror will cause a phase shift of pi

the phase is also shifted due to the path difference:

(Δr)(2pi)/λ

so total phase shift is pi + (Δr)(2pi)/λ

## The Attempt at a Solution

I can calculate interference at the point on the screen directly in front of the point source:

pi + (Δr)(2pi)/λ = pi + (0.8 mm)(2 pi) / 589 nm

but I'm not sure where to begin finding the fringe spaces on the screen. I can't come up with a function to relate interference on the screen to the path difference caused by the mirror. Any hints would be appreciated!