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Although I could understand the basics of single slit diffraction, diffraction grating seems something confusing to me.

In diffraction grating, we know there are a lot of slits within a unit length. For our convenience we consider that there are 5 slits per centimeter. Now if the source is quit far from the slits for around 5cm behind the slits,diffraction fringes will be formed on th screen. There will be a pattern of minima and maxima. If we consider two slits only then we would easily understand the presence of minimas. But this time there are many slits, so shouldn't the minima be a more bright considered to single/double slit diffraction? Since the wavelets emerging from the surrounding slits might not have that specific phase difference which would negate each others. I don't know if it is correct or not but I think the brightness of minima shouldn't be much less compared to the maxima. I know that in case of single slit diffraction the minimas do have a little bit of brightness which usually gets ignored or cannot be percieved.

Another question: Is there only one central bright maxima in case of diffraction grating or many depending on the number of slits? By central maxima I am referring to fringes with maximum brightness/intensity.

Qmechanic
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MSKB
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    Related/Duplicate? Fringe width and spacing and number of slits in diffraction experiments – Farcher May 18 '21 at 08:27
  • @Farcher your answer to that question really helped me. But it would be much more helpful if I were provided with the answer to my first question that is why don't the intensity of minima increase in multiple slit diffraction than lower number of slits? There might be many cases with in the system where wavelets emerging from some slits do no remain out of phase where minimas are determined to be present – MSKB May 18 '21 at 09:48
  • In theory for an ideal arrangement the intensity of the minima is zero. – Farcher May 18 '21 at 10:17
  • In my book equation for minima was derived based on only 2 slits though it was about grating. So I was woundering for 2 slots it might seem to be a minima. But as there are more number of slits, there might be some waves emerging from the other slits(i mean slits excluding the reference ones) might be in phase at that position where it was supposed to be a minima – MSKB May 18 '21 at 15:01
  • What happens is that the principal minima get sharper and more intense and in the region between these fringes where there was only one minimum with two slits there are a number of subsidiary maxima and an appropriate number of minima. – Farcher May 18 '21 at 15:52
  • Ohh got it.....everything in grating gets thinner and does my intuitition also plays a role in this which is basically the reason behind the minimas getting thinner – MSKB May 18 '21 at 16:42

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