.Light passes through a system of two slits with slit width of 6.9 μm and slit separation d. When the interference pattern is observed, it is noted that every 5th bright fringe is missing. What is the separation between the slits?
Original post by Muneer Hussain
.Light passes through a system of two slits with slit width of 6.9 μm and slit separation d. When the interference pattern is observed, it is noted that every 5th bright fringe is missing. What is the separation between the slits?

What you need to know is that the maxima of interference from the two slits coincide with the minima of the diffraction.
Please describe what you have done or what is troubling you in attempting the problem in future instead of just posting the problem.
i did not find anything yet i understand that missing order occue due to overlaping of maxima and minima so maxima value is for order m 4 but what is minima value and what is formula
Original post by Muneer Hussain
i did not find anything yet i understand that missing order occue due to overlaping of maxima and minima so maxima value is for order m 4 but what is minima value and what is formula

Instead of me telling what formula to use, why not you write down all the formulas for maxima for double slits interference and "all" the formula for minima for single-slit diffraction and connect them yourself.
If you have an issue, then you write down all the formulas here.
condition for missing order is : a+b / a = n/m where n is maxima for bright and n is minima for diffraction a is width of slit b is slits sepration now confussion is that if n= 4 ( 5th bright fring) then how to solve for b if a =6.9 μm , i do not know what is value of m here order of dark fring
Original post by Muneer Hussain
condition for missing order is : a+b / a = n/m where n is maxima for bright and n is minima for diffraction a is width of slit b is slits sepration now confussion is that if n= 4 ( 5th bright fring) then how to solve for b if a =6.9 μm , i do not know what is value of m here order of dark fring

You want to review what you have written.
If a+b / a = n/m is the equation for missing order and you have not made any mistake, I disagree. You may want to explain how you arrived at the equation.

Next, you can make some sketches of the interference fringes and the diffraction fringes and overlap them to deduce minimum order for diffraction.