- #1

The-Exiled

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## Homework Statement

The diameter of the 5th and 15th bright ring formed by sodium light (wavelength = 589.3nm) are 2.303mm and 4.134mm respectively. Calculate the radius of curvature.

## Homework Equations

DON'T ASSUME THAT THE RINGS ARE PERFECTLY CENTRED

(I assume that means that the radius of the rings can't be obtained by simply dividing the diameter by 2)

## The Attempt at a Solution

I am not sure how to start finding the radius of the rings or if I need it at all? I know there is a [tex]\pi[/tex] phase change and hence the constructive interference is when

2 x [distance in air] = (m + 0.5)[tex]\lambda[/tex].

I've tried finding the ratios of diameters for some reason, just to see if it lead to anything... It didn't... Can anyone help me please?

Thank you very much