Remembering Verghese Kurien “Father of White Revolution in India”

Today 26 November 2015 is the 94th birthday of Verghese Kurien popularly known as “Father of White Revolution in India”. He founded around 30 institutions of excellence (like AMUL, GCMMF, IRMA, NDDB) which are owned, managed by farmers and run by professionals. As the founding chairman of the Gujarat Co-operative Milk Marketing Federation (GCMMF), Kurien was responsible for the creation and success of the Amul brand of dairy products.

Google celebrated the 94th birthday of Verghese Kurien by this doodle


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YDSE (Young’s Double Slit Experiment)

In the question we have a simple YDSE setup , there’s just the addition of a glass slab of thickness t and ,refractive index u, in front of the top slit ( S1). Now we submerge the entire setup into water (given refractive index u1). We now have to find the locations of the points, which are the points of constructive interference( max intensity).

I considered 3 approaches, first-

I calculated the optical path difference in water = t(u/u1 -1)- yd/D. where y is the reference coordinate of the maxima( any general position) from the original central maxima, d is the slit separation , and D is the distance from screen. For constructive interference path difference = n*wavelength( in water). Now wavelength in water= “wavelength in air”/u1 Therefore we get our answer.

Approach two:

I found out the path difference in water and multiplied it by u1 , to get the path difference in air , and I got the same result when I equated this path difference to- n*wavelength(in air).

Approach three- I found the path difference in air – t(u-1)-yd/D and divided this by u1, to get path difference in water, and equated this to n* wavelength (water). This time around , I did not get the answer.

Can anyone explain the difference between the second and third approaches. And also please do tell me, if I have committed some error.

Posted by Garvit Sharma