My interview experience at IISC

In this blog I am going to write about my interview experience at IISC. It was held in offline mode this year (2022). There were three dates allotted by them for the interviews : 30th May, 31st May and 1st June. My interview was on 31st of May 2022. This year IISC called upto rank 60 for JAM and 83 in JEST. My rank in JEST was 30. So I was called through JEST. This time interview has held in two halves one started from 9 am and the other from 2 pm. My interview was from 2 pm. Although it was supposed to start from 2 pm but it got delayed. We were seated in the auditorium. We were waiting to be called.  I was called at the beginning. A professor told me to follow him. I went into a classroom. It was not too big. There were 4 professors in the room.

One of them inquired about my interests.

To which i replied Quantum mechanics, Classical mechanics, and Mathematical physics. 

(Now let me call the professors by A, B, C, D.)

Prof A : "lets start with mathematical physics."

Me : "Ok sir"

Then he asked me to go to the board and  write an equation which was like :

4x² y"-4x² y'+(1-2x) y = 0

I went to the board thought long about this equation. Then Prof A said, "tell me how are you thinking to solve this ?". I fumbled a bit. But he was kind enough to help me 

Prof A : "you can use series solutions method to solve this. Have you studied that? "

I said, "yes but I studied that long ago so I don't remember much"

He said me to write y= Σ  an x^(n+r)

Then i used that equation and solved 

Prof A: "what is the coefficient of the lowest power of x ? "

I wrote that on the board and found out the roots. (they were equal roots)

Prof A : "Why there is only one solutions? What will you do to find the other solution?"

Me: "Since this is a 2nd order differential equation we will have two independent solutions"

Prof A : "Tell me how will you find the other solution"

I stumbled over the words and by the time Prof A said to move on to the next question.

Now Prof B starts......

Prof B : "Write down the most general form of Schrodinger Equation"

I wrote : (again another mistake 😅)

H ψ = E ψ

Prof B: "Is that the most general equation ?"

I looked again found that i mistakenly wrote the time independent equation (holy shit...)

I hurriedly rubbed the equation and wrote:

H ψ = ih∂ψ/∂t

Prof B : "Now it is Ok"

Next they asked me

let Φ=Û(t) Ψ 

Now find the Hamiltonian 

It was easy I just inserted Φ  on the right hand side of the equation and did some calculations :

What they wanted me to was to eliminate Ψ and write that equation in terms of Φ.

They also gave me few hints in between so I did that very easily.

Almost done.....

So yeah, I completed it. They were satisfied with the answer (I saw Prof B's grinning)

Now comes Prof C 

Prof C: " So Debankur tell me what experiments were done in your college?"

Me: " Sir, due to covid our college was closed for about 2 years so almost no experiments were done"

Prof C: "Its the same with everyone. Tell me the one's you did"

Me : "I did few experiments in Semester 1"

Prof C: "What did you do? Do you remember something?"

Me : "Something pendulum-type was there" (LOL 🤣)

Prof C: "Ok I'll ask you from that part"

He told me to write down the expression for time period of a simple pendulum

and I did:

Prof C: "Ok. Now tell me what will be the error in measuring time if I know the error in measurement of length"

So I did this:

He said it was ok.

Prof C: "Tell me how do I measure the value of g in this room if you are given the length and the mass of the bob"

Me: "I'll hang the pendulum at the ceiling calculate its length and since mass is given. And I'll calculate the time it takes for 10 or 20 oscillations and then find out the value of g in the room by putting the value of T in that equation"

Prof C: "This method will give you error.  Can you do something to make the experiment more accurate?"
I said many foolish answers. Then I asked, "I am I allowed to change the length of the pendulum?"

Prof C: "Yes then what you will do?"

The way he said that confirmed me that I was on the right track (😅)

Me: "I will take a pendulum and each time I will increase the length of the pendulum and calculate the time period of the new length and then plot the graph of T vs l"

Prof C: "Can do show how will the graph look like?"

I then drew the following graph:

Prof C: "Can you still do something to make this graph more accurate?"

I mumbled some nonsensical answer. They again asked me what I said. I was petrified.

Now Prof B gave me some hints 

Prof B: "What was the first equation you have learned in your life"

Me: "A linear equation"

Having said this I understood what they were hinting at

Then I did this: 

They said it was right

Me: 😇

Next Prof D asked me a question

Prof D: "If I hang a pendulum here can you draw the trajectory of the bob on a horizontal plane?"

I drew this: (although wrong)

Prof D: "This is not right. Remember the earth is rotating"

I thought for a while. Then I said, "will the curve be like the one we see in a Foucault's pendulum?"

Prof D: "Can you draw how will it look like?"

Then I drew this :(LOL 🤣)

Prof D: "The drawing is horrible but the idea is correct" (🤣)

In this way my interview ended. It took about 40 minutes.

On 7th of June the list of selected candidates were announced. And I got selected.

I received the call letter on 11th of June.

Although they did not publish the result in their website. I hope soon they will update their website.