# Interference - Single slit diffraction

1. Nov 2, 2015

### Isaac Pepper

< Mentor Note -- thread moved to HH from the technical physics forums, so no HH Template is shown >

Hi guys, I have a question here which I'm struggling to do and perhaps you could help ;

Monochromatic electromagnetic radiation with wavelength λ from a distant source passes through a slit. The diffraction pattern is observed on a screen 2.50 m from the slit.
If the width of the central maximum is 6.00 mm, what is the slit width a if the wavelength is 500 nm (visible light)?

What I have done is

y=(R(m+1/2)lambda) / d where y = 3mm (half of the central maximum width); R = 2.5m m = 0 lambda=500nm

d =( R(m+1/2)lambda) / y

d =( 2.5 * (1/2) * 500x10^-9 )/ 3x10^-3
and so I manage to obtain d = 2.08x10^-4 m, however this answer is wrong

what am I doing wrong?
Thanks !

Last edited by a moderator: Nov 2, 2015
2. Nov 2, 2015

### BvU

Hello Isaac, welcome to PF !

This looks an awful lot like homework, so better post it there. You get thrown in a useful template as an extra !

You sure you are applying an equation for a single slit diffraction pattern ?

3. Nov 2, 2015

### Isaac Pepper

I shall do, thanks :)

4. Nov 2, 2015

### Staff: Mentor

Don't re-post; I will move it there now...

5. Nov 2, 2015

### Isaac Pepper

Thanks ! I have worked it out and I was indeed using the 2-slit diffraction formula :/

The answer was 4.167x10^-4

6. Nov 2, 2015

### BvU

Well done ! Hope to see you back some time in the future, but don't hurry...