Diffraction With A Single Slit And A Lens.

[chris_avfc]

Homework Statement

Trying to find the number of diffraction maxima and the width of the whole pattern.
\lambda = 500nm
b = 2.8μm (Slit Width)
f = 100mm
r = 25mm
L = 25mm (Slit to Lens)

Homework Equations

I have the worked out the irradiance formula as:

I(\theta)=I_0 sin^2(\beta)/(\beta^2)

The conditions for minima

b sin\theta = m\lambda

Angular width of central fringe

\Delta\theta \approx 2\lambda/b

Width of central fringe

W \approx 2L\lambda/b

The Attempt at a Solution

As said I worked out the irradiance formula, and I think to find the width of the whole pattern you would do:

(Fringe Width \times 2) + 1

As then it accounts for the dark fringes as well, plus the one extra for the central.

As for working out the number of maxima, I would guess it would involve the condition for a minimum as it contains the order of diffraction.

What really throws me off though, is the lens, I'm not sure what that would do for the calculations.

 

[chris_avfc]

Sorry to bump this, but does anybody have any idea?

 

[chris_avfc]

Going to be a pain and see if anyone can help me again?

Can't get anywhere with this. :(