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

A parallel beam of mono-chromatic light (500nm) is incident on 2 long narrow slits: slit width is 0.1mm and the distance between slit centres is 0.3mm.

a) How many bright fringes cover the central diffraction maximum?

2. Relevant equations

Condition for constructive interference:

[tex]\Delta = 2d.cos\theta = 2m(\lambda\div2)[/tex]

Reduces to:

[tex]2d=m\lambda[/tex] as [tex] cos\theta=1[/tex] ?

3. The attempt at a solution

I get 1200 once I convert both[tex] d [/tex]and [tex]\lambda[/tex] into metres. Is this the right thing to do? I'm not sure this is the amount that cover the central maximum, what does this bit mean?

- - - Part b)

1. The problem statement, all variables and given/known data

Part b) Calculate the angle corresponding to the first diffraction minima

2. Relevant equations

[tex]sin\theta= ((2m-1)\lambda)\div2)\div d [/tex]

3. The attempt at a solution

Taking m as 1 because it is the first diffraction minima

Reduces to:

[tex]\theta = arcsin[ (5\times10^{-7}) / (6\times10^{-4}) ][/tex]

I get [tex]\theta[/tex] = 0.048 degrees

is this correct?

There is part c) but haven't attempted it yet, overall the whole question is allocated 14 marks.

1. The problem statement, all variables and given/known data

2. Relevant equations

3. The attempt at a solution

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# Homework Help: Double Slit Diffraction fringes

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