I.. F<mT SERVICE P (EXAM}-..014



I


PHYSICS

Paper-II

ITime allowed Three Hours I IMaximum Marks 200 I
1

Question Paper Specific Instructions

•
Please read each of the following instructions carefully before attempting
questions:
Th..re are EIGHT questions in all out of whi.ch FIVE are to be attempted.

Questions no. 1 and 5 are compulsory. Out of the remaining SIX questwns, THREE are to
be attempted selecting at least ONE question from each of the two Sectwns A and B.
Attempts of questions shall be counted in chronologi.cal order. Unless struck off, attempt of


a QU(!Stion shall be counted even if attempted partly. Any page or portwn of the page left


blank in the Question-cum-Answer Booklet must be clearly struck off.
All questwns carry equal marks. The number of marks carried by a question I part is
indicated against it.



Answers must be written in ENGLISH only.
Unless otherwise mentioried, symbo/s and notations have their usual standard meanings.
Assume suitable data, if riecessary and indicate the same clearly.
Neat sketches may be drawn, wherever required.



List of Useful Constants
Mass of proton
Mass of neutron
Mass of electron


Planck constant 6•626 X 10-34 JS
Boltzmann constant 1 ·380 X 10-23 JK.'""1

Bohr magneton
Nuclear magneton

Electronic charge
Atomic mass unit

g.. 5·5855 µN
1 ·00866 u
12·00000 u
iH) 2·014022 u

9·273 x 10-24 A m2
5·051 x 10-27 n-1
1 ·602 x 10-19 C
1 •660 X 10-27 kg

931 MeV
1·00727 u
..He) 4·002603 u
86·908893 u
3·0160500 u


C-HENT-N-YPNM B
1


..

SECTION A


l

Ql. Answer all of the folowing
8x5=40

I What is the de B..oglie wavelength of an electron whose kinetic energy is 100 eV?
Normalize the ..ound state wave function
A .
-for the simple harmonic oscillator and find expectation values x and

An atom in an e..cited state of 4·7 eV emits a photon and en_ds up in the ground state. The lifetime of the excited state is 10-13 s. Calculate the energy uncertainty and obtain the spectral line width in wavelength of
photon.
What is Lamb shift? How is it measured?
Given that the. rotational inertia of HCl molecule has the value I 2·66 x 10--41 kg-m2
estimate the energy difference between the lowest and first excited state of HCl. 8
Q2. Derive an expression for transmission coefficient for a particle through a rectangular pote..tial barrier. 20
Using WKB appr6ximation find out the lifetime of a-emitter. 20.
Q3. Show that
two o t e t ree components o angu ar momentum operator
commute ahd 10
the third . component of the angular momentum operator
commutes irith the square of angular momentum operator. 10
Discuss the diffdrent coupling schemes in atomic spectroscopy with suitable diagrams. 10
Explain the origid of the anomalous Zeeman effect. 10
q4.(a)Explain spin-sp1n and spin-lattice relaxation times in NMRspectroscopy. How do they influence the line width of the NMR line? 10

How is proton mkgnetic resonance applied to determine the chemical shifts in molecuIJs containing hydrogen atom Illustrate your answer with a suitable exkmple. . What are the characteristics of a Raman spectrum How do you ·study
Raman spectra in the laboratory Give two applications of Raman effect. I 20

SECTIONB
Q5. Answer all of the following 8x5=40

2714si and. 27 13Al are mirror. nuclei. Their ground states areidentical except the charge. If their mass difference is 6 MeV, estimate their radius neglecting the proton-neutron mass difference. 8

Calculate the energy released per gram offu,el for the nuclear reaction 8
2H 21H l1H

Explain why each of the following reactions is forbidden: 8


p p p +pie4+ y

0 n pie°
ve+
v e
X-ray of wavelength 1·4 A is found to be Bragg reflected from plane of an fee structure. If the lattice parameter of the crystal is 5 find the angle at which the X-ray beam is incident on the plane of the crystal. 8
A silicon diode operates at a forward bias voltage of 0·4 V. Calculate the "!factor by which the current will be multiplied when the temperature is increased from 25°C to 150°C (ri for Si= 2). 8
Q6.(a) How does the semi-empirical mass formula explain the stability of a nucleus against beta decay 20

Briefly explain the meson theory of nuclear force. 10
What are the major components of a fission reactor With a schematic
diagram explain its working. 10
Q7. Explain in .detail the -classification of elementary particles. 20

What is ac Josephson effect . Derive an expression for the cqr:rent flowing through .the junction formed by two superconducting films
separated by an insulator. ..(J

Q8.(a) Explain with the help of a neat diagram· the structure of a n-channel FET and its IV bharacteristics. In what way is an FET different from a BJT? 20

Show that the J gate is a universal gate. 10

For the logical equation given below, form the truth table and draw the correspo..ding logic circuit using different gates 10

Y=A.B +A.B