(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

I have some difficulty understanding a part of the following problem:

In Young’s experiment, narrow double slits 0.20 mm apart diffract monochromatic light onto a screen 1.5 m away. The distance between the 5th minima on either side of the zeroth-order maximum is measured to be 34.73 mm. Determine the wavelength of the light.

2. Relevant equations

Here is a diagram of the double slit experiment:

http://imageshack.us/scaled/landing/850/doubleslit.jpg [Broken]

Condition for minima: ##d \ \sin \theta = (m+\frac{1}{2}) \lambda##

Linear positions measured along the screen: ##\tan \theta = \frac{y}{L}##

##\therefore \ y_{dark} = \frac{L (m+\frac{1}{2})\lambda}{d}##

3. The attempt at a solution

So, in the question what is meant by "distance between the 5th minima on either side of the zeroth-order maximum"? I'm not sure if I understand this.

Does this mean the distance from the 5th minima on one side of the maxima to the 5th minima on the other side like this:

http://imageshack.us/scaled/landing/706/52496318.jpg [Broken]

Did I understand the question correctly? If this is correct, then

##34.73=2y \implies y=17.37 \ mm##

And I can find the λ by rearranging the above equation:

##\lambda=\frac{y \ d}{L(m+\frac{1}{2})} = \frac{(17.365\times 10^{-3})\times (0.2 \times 10^{-3})}{1.5(5+\frac{1}{2})} = 4.2096 \times 10^{-7}##

Is this correct? The answer looks reasonable (about 420.96 nm in the blue/violet region of spectrum), but I doubt it is correct. Any help would be greatly appreciated.

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# Homework Help: Optics (double slit experiment)

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