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- Homework Statement
- One of the beams of an interferometer passes through a small evacuated glass container 1.155 cm deep. When a gas is allowed to slowly fill the container, a total of 177 dark fringes are counted to move past a reference line. The light used has a wavelength of 632.1 nm .

- Relevant Equations
- n(gas) = 1 + [m(lambaair)]/(2*t)

hi,

i understand how to get to this equation, and this is the equation that gives the answer. However, the question asks for dark fringes which is destructive interference? would you not use m/2? so instead of the denominator (2*t) would it not be (4*t)?

thanks in advance!

i understand how to get to this equation, and this is the equation that gives the answer. However, the question asks for dark fringes which is destructive interference? would you not use m/2? so instead of the denominator (2*t) would it not be (4*t)?

thanks in advance!