Here is a summary of the questions which has possibly been set wrong (I have given details below) or numerical answer types whose answers have been given incorrectly as per the declared answer sheet.
Q8. The magnetic field also has a odd parity. Not “E and A only”. Since that choice (or “none of the above”) isn’t given, clearly the question has been set wrong. See here.
Q3. The Stern-Gerlach experiment evidenced space quantification of angular momentum. The Zeeman effect evidenced the existence of electron spin. That choice isn’t given, instead answer sheet gives the opposite as the correct answer. See any good text on quantum mechanics. eg “Quantum Mechanics 2nd edition, Bransden, Joachain” page: 37 and 38. To avoid any ambiguity, Its the S-G experiment which evidences space quantization (of both spin and orbital angular momentum). But Zeeman effect evidences electron spin only. It was the anomalous Zeeman effect which had led to the discovery of electron spin.
There are also two NAT type questions which seems to be way off in the correct responses as per the exam conducting body. But the calculations shows somebody missed something somewhere. They are questions 48 and 49 according to the uploaded answer sheet and question paper. I have performed the detailed calculations in this pdf file: gatephysics_2018.
Altogether this is 6 marks and 2/3 marks for the Q3 and Q8 if they have been deducted wrongly. So, 6+2/3 marks. I haven’t been able to find any more lapses although it was very tempting to feel so.
I think the above question asked in GATE 2018 (physics) is wrong.
Any vector has two components. The component perpendicular to the parity axis has even parity and the parallel component to the axis has odd parity.
The opposite is true for axial vectors.
E, A vectors.
B, L axial vectors.
The correct answer per gate exam body is E, A. Why not B and L? It’s an arbitrary situation and perpendicular components of these fields will have odd parity.
So the question since it does not specify the direction might be wrong. Unless I’m missing anything. What’s your idea ?
I am adding one relevant page for why the answer might be wrong. (A question is wrong, when all possible answers given are, wrong. That seems to be the case here.) For detailed answer and any other relevant page, check here. [Prof. S. Errede’s handouts. UIUC]
According to this lecture note from a famous university (UIUC) among E, B, L and A except L all others have odd parity. L doesn’t as its made from cross product of two vectors (r and p) which both have odd parity. There are several ways to see why B has odd parity as well. One is to see it as B = curl A. A has odd parity and grad operator has even parity. Check page 5 of the linked note from UIUC.
So except L all others have odd parity. [E, B and A]. Putting the phrase “only” makes the question erroneous. Because e and A pair is right but its not the only ones among the given vectors which has odd parity.
Nuclear and particle physics through Scilab. More…
Reminiscing a dreadful day in my life. Today 16th April, a decade ago, 2007.
It was early morning. Snow flakes were making the surrounding really beautiful. Especially because I was sitting inside of a cozy air conditioned student center, looking out of the glass wall. The hazelnut flavored milk-less coffee used to be one of my favorite, especially when I would be sitting alone. I was reading a paper on “phenomenology of quantum mechanical phases related to my thesis research”. These were the days I had started writing or at-least musing about writing blogs. So I was even perhaps in the mood of writing a poem or something.
The beautiful silence was broken by a strange noise of a crowd. I looked around. A man with a long gun, as long perhaps as himself, of-course a bit smaller, wielding it to the ground was hailing at the folks around “stay indoor”. More…
Optics Series Lecture, Lecture – XIV, XV, XVI.
“Color of thin films, Newton’s rings, Lloyd’s mirror and Phase changes during reflection” These lecture were delivered on 16th February, 21st February and on 17th March. The lecture sessions were of 1 and 1/2 hours. The lectures were delivered to both Physics honors as well as Physics elective students on different days.
We have previously discussed what is interference and what is wave-front splitting and amplitude splitting interference. We have also discussed in much details two wave-front splitting interference viz. Young’s double slit interference (Lecture – IX) and Fresnel’s bi-prism (Lecture – XI). Today we will discuss one more wave-front splitting interference namely Lloyd’s mirror interference before moving onto the amplitude splitting interference of the Newton’s Rings. Also we will discuss two interesting and related concepts; i. Phase change on reflection and ii. Color of thin films. More…