# Homework Help: Not getting what this question wants to say

1. Dec 18, 2012

### dreamz25

Not getting what this question wants to say!!!

1. Two slits are made one millimetre apart and the sreen is placed one metre away. What should the width of each slit be to obtain 10 maxima of the double slit pattern within the central maximum of the central slit pattern?

My problem is that that i am not getting what this problem wants..

If someone could explain it to me briefly as this problem is important for me to work out...!!

2. Dec 19, 2012

### rude man

Re: Not getting what this question wants to say!!!

There are two things going on here: interference between the wavefronts emerging from the two slits, and diffraction by each slit separately. Interference produces the two-slit pattern and is not a function of the slit widths. The diffraction pattern is separately produced by each slit , and here the slit width does come into play.

The two-slit pattern is straight-forward. See your inroductory physics text. But the diffraction pattern should (I suppose) be separately calculated for each slit, and then the two diffraction patterns superimposed on the screen.

I have a feeling one can cheat and just consider one of the slits as producing the central maximum region. That would again produce a standard textbook single-slit pattern.

The width of the central pattern would be inversely proportional to the slit width. Your job is to compute the slit width such as to give a central (diffraction) width equal to 10 interference maxima across the screen.