help-2444110_1920 (1)

IMSc, Chennai -IPhD interview experience- Sayan Mondal | Physics After Engineering blog


    So  let me share with you my Institute of Mathematical Science, Chennai interview experience. I didn’t have a particularly good interview, so I’m not expecting getting selected in this. There were 3 professors let’s call them A, B and C.
Prof A gave me a choice between Electrodynamics and Differential Equations.
I chose Electrodynamics.

A: Write Maxwell’s Equation.

I wrote them on the board.

A: now please remove the Maxwell correction term. And tell me if the equations are consistent.

Me: I tried to explain to them using the capacitor description that we were taught in Class 11-12. He listened to it and said to me that it is correct but asked me to show it through the four equations.
I was struggling, so Prof. C gave me some hint: take divergence on the equations and I did so. After struggling a bit, at last, I arrived to the conclusion that the charge flow is not being conserved, so we need Maxwell’s correction.   

Prof A now gives me the E and B components of an EM plane wave. He wrote them like this:

B= B0 ei(k’.r-w’t) (k’,B0 are vectors btw),(here there is k’ and w’)

E=E0ei(k.r-wt) (here there is k and w)

He asked me to

Prove k’=k and w’ = w.

I tried proving by putting them into the Maxwell equation but couldn’t finish, so they moved onto the next question.

Prof B now asked me about Quantum Mechanics.

B: Draw the 1D infinite well potential.

I did so.

B: write the Wavefunctions and energy values. (Energy Eigenstate and value)

I did so.

B: Now draw the 3rd eigenstate.

I did so.

B: Now imagine If the base wasn’t horizontal but slanting (like y=x), then how will the eigenstate change?

B: Give me the qualitative picture.

Me: Since k is dependent on E-V and this gets lower so K decreases and wavelength increase also the wavefunction amplitude is lower at higher V.

Then Prof C asked me if

The first Half cycle (the part between  x=0 and first node) of this modified V(x) have a bigger or smaller amplitude than the first half cycle of the normal particle in the box.

I struggled a bit, she gave a hint that it can be obtained by the property of wavefunctions.
I realized that

 The total Probability will be 1 and since the two other part has lower amplitude this will compensate and hence will be bigger, 

She agreed.

Then Prof C asks me a question on Classical Mechanics.

C: A particle is thrown up in a resistive medium where Fres depends on v.

I wrote the force equation.

C: What would be the velocity at time t->infinity.

ME: it will depend on the initial velocity.

C: Write the force equations in terms of v and solve the differential equation 

I did so and got an exponentially decaying function with a constant term.

Me: The velocity is constant at t->infinity as at some point the resistive force gets equal to mg and the ball has not acceleration so the ball is traveling in constant speed.

C: what is this velocity called?

Me: Critical Velocity? (I couldn’t recall the term)

C: No It is called Terminal Velocity.

                The interview ended here. The professors were super nice and gave hints at every point when I was struggling. IMSc is also a great institute.  Also, they provided free accommodation and Travel expenses. Food was really good and at a decent price.

RESULT : Not Selected(Wait Listed).

Here are some other questions that were asked to other people :

  • Cycloid motion and Cyclotron motion of charged particle derivation. (This was not asked directly but the result arrived after successive questions on Lorentz force and diff equations)
  • A loop which is cutting a B field pulling a mass and when there is flux changing the block is moving down until the flux in a loop starts changing again. Leading to a Periodic motion. something of that sorts. So, the questions were quite doable.

Leave a Comment

Your email address will not be published.

Soham Sau’s Journey

I was not a typical good student as seen in the Indian education and social system and I still not am, but, I have always believed in hard work, endurance

Read More »

Types of UG Biology courses

BSc Honours 3-year course. Most widely accepted and preferred undergraduate degree for someone doing basic sciences. B.Sc Hons. courses give the student the opportunity to specialize in their chosen subject.

Read More »

Architecture at a glance

If you wonder why Architecture is important, just look around. You are likely to be surrounded by it. We grew up appreciating something as trivial as the play of light,

Read More »