CBSE Class 12 Physics Question Paper 2020 Set 55-2-3

H$moS> Z§.
Code No. 55/2/3
amob Z§.
Roll No.

ZmoQ> NOTE
(I) H¥$n`m Om±M H$a b| {H$ Bg àíZ-nÌ _o§ _w{ÐV (I) Please check that this question
n¥ð> 19 h¢ & paper contains 19 printed pages.

(II) àíZ-nÌ _| Xm{hZo hmW H$s Amoa {XE JE H$moS (II) Code number given on the right
>Zå~a H$mo N>mÌ CÎma-nwpñVH$m Ho$ _wI-n¥ð> na hand side of the question paper
{bI| & should be written on the title page of
the answer-book by the candidate.
(III) H¥$n`m Om±M H$a b| {H$ Bg àíZ-nÌ _| (III) Please check that this question
>37 àíZ h¢ & paper contains 37 questions.
(IV) H¥$n`m àíZ H$m CÎma {bIZm ewê$ H$aZo go (IV) Please write down the Serial
nhbo, CÎma-nwpñVH$m _| àíZ H$m H«$_m§H$ Number of the question in the
Adí` {bI| & answer-book before attempting it.
(V) Bg àíZ-nÌ H$mo n‹T>Zo Ho$ {bE 15 {_ZQ >H$m (V) 15 minute time has been allotted to
g_` {X`m J`m h¡ & àíZ-nÌ H$m {dVaU read this question paper. The
nydm©• _| 10.15 ~Oo {H$`m OmEJm & question paper will be distributed
10.15 ~Oo go 10.30 ~Oo VH$ N>mÌ Ho$db at 10.15 a.m. From 10.15 a.m. to
10.30 a.m., the students will read the
àíZ-nÌ H$mo n‹T>|Jo Am¡a Bg Ad{Y Ho$ Xm¡amZ question paper only and will not
do CÎma-nwpñVH$m na H$moB© CÎma Zht {bI|Jo & write any answer on the
answer-book during this period.

^m¡{VH$ {dkmZ (g¡ÕmpÝVH$)
PHYSICS (Theory)

{ZYm©[aV g_` : 3 KÊQ>o A{YH$V_ A§H$ : 70
Time allowed : 3 hours Maximum Marks : 70

.55/2/3 1 P.T.O.

gm_mÝ` {ZX}e :
{ZåZ{b{IV {ZX}em| H$mo ~hwV gmdYmZr go n{‹T>E Am¡a CZH$m g™Vr go nmbZ H$s{OE :
(i) Bg àíZ-nÌ H$mo Mma IÊS>m| _§| {d^m{OV {H$`m J`m h¡ – H$, I, J Am¡a K &
(ii) Bg àíZ-nÌ _| 37 àíZ h¢ & g^r àíZ A{Zdm`© h¢ &
(iii) IÊS> H$ – àíZ g§»`m 1 go 20 VH$ A{V bKw-CÎmar` àíZ h¢, àË`oH$ àíZ 1 A§H$ H$m
h¡ &
(iv) IÊS> I – àíZ g§»`m 21 go 27 VH$ bKw-CÎmar` àíZ h¢, àË`oH$ àíZ 2 A§H$m| H$m h¡ &
(v) IÊS> J – àíZ g§»`m 28 go 34 VH$ XrK©-CÎmar` àíZ h¢, àË`oH$ àíZ 3 A§H$m| H$m h¡ &
(vi) IÊS> K – àíZ g§»`m 35 go 37 VH$ ^r XrK©-CÎmar` àíZ h¢, àË`oH$ àíZ 5 A§H$m| H$m h¡ &
(vii) àíZ-nÌ _| H$moB© g_J« {dH$ën Zht h¡ & VWm{n, EH$-EH$ A§H$ Ho$ Xmo àíZm| _|, Xmo-Xmo A§H$m|
dmbo Xmo àíZm| _§o, VrZ-VrZ A§H$m| dmbo EH$ àíZ _§o VWm nm±M-nm±M A§H$m| Ho$ VrZm| àíZm| _§o
Am§V[aH$ {dH$ën {X`m J`m h¡ & Eogo àíZm| _| Ho$db EH$ hr {dH$ën H$m CÎma Xr{OE &
(viii) BgHo$ A{V[aº$, Amdí`H$VmZwgma, àË`oH$ IÊS> Am¡a àíZ Ho$ gmW `Wmo{MV {ZX}e {XE JE
h¢ &
(ix) H¡$ëHw$boQ>a AWdm bm°J Q>o~b Ho$ à`moJ H$s AZw_{V Zht h¡ &
(x) Ohm± Amdí`H$ hmo, Amn {ZåZ{b{IV ^m¡{VH$ {Z`Vm§H$m| Ho$ _mZm| H$m Cn`moJ H$a gH$Vo h¢ :
c = 3  108 m/s
h = 6.63  10–34 Js
e = 1.6  10–19 C
0 = 4  10–7 T m A–1

0 = 8.854  10–12 C2 N–1 m–2
1
= 9  109 N m2 C–2
4 
0

BboŠQ´>m°Z H$m Ðì`_mZ (me) = 9.1  10–31 kg
Ý`yQ´>m°Z H$m Ðì`_mZ = 1.675  10–27 kg
àmoQ>m°Z H$m Ðì`_mZ = 1.673  10–27 kg
AmdmoJmÐmo g§»`m = 6.023  1023 à{V J«m_ _mob
~moëQ²>µO_mZ {Z`Vm§H$ = 1.38  10–23 JK–1
.55/2/3 2

General Instructions :
Read the following instructions very carefully and strictly follow them :
(i) This question paper comprises four Sections – A, B, C and D.
(ii) There are 37 questions in the question paper. All questions are
compulsory.
(iii) Section A – Questions no. 1 to 20 are very short answer type questions,
carrying 1 mark each.
(iv) Section B – Questions no. 21 to 27 are short answer type questions,
carrying 2 marks each.
(v) Section C – Questions no. 28 to 34 are long answer type questions,
carrying 3 marks each.
(vi) Section D – Questions no. 35 to 37 are also long answer type questions,
carrying 5 marks each.
(vii) There is no overall choice in the question paper. However, an internal
choice has been provided in 2 questions of 1 mark, 2 questions of
2 marks, 1 question of three marks and all the 3 questions of five marks.
You have to attempt only one of the choices in such questions.
(viii) In addition to this, separate instructions are given with each section and
question, wherever necessary.
(ix) Use of calculators and log tables is not permitted.
(x) You may use the following values of physical constants wherever
necessary :
c = 3  108 m/s
h = 6.63  10–34 Js
e = 1.6  10–19 C
0 = 4  10–7 T m A–1

0 = 8.854  10–12 C2 N–1 m–2
1
= 9  109 N m2 C–2
4 
0

Mass of electron (me) = 9.1  10–31 kg

Mass of neutron = 1.675  10–27 kg
Mass of proton = 1.673  10–27 kg
Avogadro’s number = 6.023  1023 per gram mole
Boltzmann constant = 1.38  10–23 JK–1

.55/2/3 3 P.T.O.

IÊS> H$
ZmoQ> : ZrMo {XE JE àË`oH$ àíZ _| g~go A{YH$ Cn`wº$ {dH$ën Mw{ZE :
1. {H$gr MmbH$ na AZwà`wº$ {H$gr {Z`V {d^dmÝVa Ho$ {bE _wº$ BboŠQ´>m°Zm| H$s Andmh
Mmb, {ZåZ{b{IV _§o go {H$g na {Z^©a Zht H$aVr h¡ ? 1
(A) MmbH$ _o| _wº$ BboŠQ´>m°Z KZËd
(B) BboŠQ´>m°Zm| H$m Ðì`_mZ
(C) MmbH$ H$s bå~mB©
(D) MmbH$ H$m Vmn
2. {ZåZ{b{IV _§o go Amo_ Ho$ {Z`_ H$m nmbZ {H$gHo$ Ûmam {H$`m OmVm h¡ ? 1
(A) ~mø AY©MmbH$m| Ûmam
(B) Z¡O AY©MmbH$m| Ûmam
(C) {ZåZ Vmn na YmVwAm| Ûmam
(D) Cƒ Vmn na YmVwAm| Ûmam
3. Am¡fY ({M{H$Ëgm) _| {ZXmZ Ho$ gmYZ Ho$ ê$n _| Cn`moJ hmoZo dmbr {dÚwV² -Mwå~H$s` Va§J| h¢ 1
(A) X-{H$aU| &
(B) nam~¢JZr {H$aU| &
(C) Adaº$ {H$aU| &
(D) namlì` Va§J| &
4. {H$gr Ymamdmhr grYo MmbH$ H$mo {H$gr EH$g_mZ Mwå~H$s` joÌ _o| aIm J`m h¡ & Bg MmbH$
H$s à{V EH$m§H$ bå~mB© na H$m`©aV ~b V~ 1
(A) A{YH$V_ hmoJm O~ MmbH$ Mwå~H$s` joÌ H$s {Xem Ho$ bå~dV² h¡ &
(B) A{YH$V_ hmoJm O~ MmbH$ Mwå~H$s` joÌ H$s {Xem Ho$ AZw{Xe h¡ &
(C) {ZåZV_ hmoJm O~ MmbH$ Mwå~H$s` joÌ H$s {Xem Ho$ bå~dV² h¡ &>
(D) {ZåZV_ hmoJm O~ MmbH$ Mwå~H$s` joÌ H$s {Xem go 45 H$m H$moU ~ZmVm h¡ &
5. {H$gr J{Verb g_Vb {dÚwV²-Mwå~H$s` Va§J _§o, {ZåZ{b{IV _§o go {H$ZH$m Am¡gV _mZ
eyÝ` hmoVm h¡ ? 1
(A) Mwå~H$s` D$Om© Am¡a {dÚwV² D$Om©
(B) Mwå~H$s` joÌ Am¡a {dÚwV² joÌ
(C) Mwå~H$s` D$Om© Am¡a Mwå~H$s` joÌ
(D) {dÚwV² D$Om© Am¡a {dÚwV² joÌ
.55/2/3 4

SECTION A
Note : Select the most appropriate option from those given below each
question :

1. For a fixed potential difference applied across a conductor, the drift speed
of free electrons does not depend upon 1
(A) free electron density in the conductor.
(B) mass of the electrons.
(C) length of the conductor.
(D) temperature of the conductor.

2. Ohm’s law is obeyed by 1
(A) extrinsic semiconductors.
(B) intrinsic semiconductors.
(C) metals at low temperature.
(D) metals at high temperature.
3. Electromagnetic waves used as a diagnostic tool in medicine are 1
(A) X-rays.
(B) ultraviolet rays.
(C) infrared radiation.
(D) ultrasonic waves.
4. A straight current carrying conductor is placed inside a uniform magnetic
field. The force per unit length acting on the conductor is 1
(A) maximum when the conductor is perpendicular to the direction of
magnetic field.
(B) maximum when the conductor is along the direction of magnetic
field.
(C) minimum when the conductor is perpendicular to the direction of
magnetic field.
(D) minimum when the conductor makes an angle of 45 with the
direction of magnetic field.
5. In a travelling plane electromagnetic wave, which of the following have
zero average value ? 1
(A) Magnetic energy and electric energy
(B) Magnetic field and electric field
(C) Magnetic energy and magnetic field
(D) Electric energy and electric field

.55/2/3 5 P.T.O.

6.  j` _§o 1
(A) Ý`yQ´>m°Z EopÝQ>Ý`yQ´>rZmo CËg{O©V H$aHo$ àmoQ>m°Z _| n[ad{V©V hmo OmVm h¡ &
(B) Ý`yQ´>m°Z Ý`yQ´>rZmo CËg{O©V H$aHo$ àmoQ>m°Z _| n[ad{V©V hmo OmVm h¡ &
(C) àmoQ>m°Z EopÝQ>Ý`yQ´>rZmo CËg{O©V H$aHo$ Ý`yQ´>m°Z _| n[ad{V©V hmo OmVm h¡ &
(D) àmoQ>m°Z Ý`yQ´>rZmo CËg{O©V H$aHo$ Ý`yQ´>m°Z _| n[ad{V©V hmo OmVm h¡ &
7. {H$gr BboŠQ´>m°Z H$mo {dam_ go {H$gr Eogo joÌ _| _wº$ {H$`m J`m h¡ Ohm± EH$g_mZ {dÚwV² Am¡a
Mwå~H$s` joÌ EH$-Xÿgao Ho$ g_mÝVa H$m`©aV h¢ & `h BboŠQ´>m°Z 1
(A) {H$gr gab aoIm _§o J{V H$aoJm &
(B) {H$gr d¥Îm _| J{V H$aoJm &
(C) pñWa ahoJm &
(D) g{n©bmH$ma nW _| J{V H$aoJm &
8. gmå` _| {H$gr p-n g§{Y S>m`moS> _o| ZoQ> Ymam hmoVr h¡ 1
(A) ~hþg§»`H$ Amdoe dmhH$m| Ho$ {dgaU Ho$ H$maU &
(B) Aënm§e Amdoe dmhH$m| Ho$ Andmh Ho$ H$maU &
(C) eyÝ` Š`m|{H$ {dgaU Am¡a Andmh YmamE± g_mZ Am¡a {dnarV hmoVr h¢ &
(D) eyÝ` Š`m|{H$ Amdoe dmhH$m| _| H$moB© ^r g§{Y H$mo nma Zht H$a nmVo h¢ &
9. {H$gr n-àH$ma Ho$ AY©MmbH$ _| XmVm D$Om© ñVa pñWa hmoVm h¡ 1
(A) D$Om© AÝVamb Ho$ Ho$ÝÐ na &
(B) MmbZ ~¡ÊS> Ho$ R>rH$ ZrMo &
(C) g§`moOH$Vm ~¡ÊS> Ho$ R>rH$ D$na &
(D) MmbZ ~¡ÊS> _| &
10. O~ Xmo Zm{^H$ (A  10) EH$-Xÿgao Ho$ gmW g§J{bV hmoH$a EH$ ^mar Zm{^H$ ~ZmVo h¢, Vmo 1
(A) ~§YZ D$Om© à{V Ý`ypŠbAm°Z _| d¥{Õ hmoVr h¡ &
(B) ~§YZ D$Om© à{V Ý`ypŠbAm°Z _| H$_r hmoVr h¡ &
(C) ~§YZ D$Om© à{V Ý`ypŠbAm°Z _| H$moB© n[adV©Z Zht hmoVm &
(D) Hw$b ~§YZ D$Om© KQ> OmVr h¡ &
ZmoQ> : Cn`wº$ CÎma go [aº$ ñWmZm| H$s ny{V© H$s{OE :
11. {Zdm©V _| {H$Ýht Xmo {~ÝXþAm| Ho$ ~rM {d^dmÝVa Vo h¡ & `{X {Zdm©V H$mo namd¡ÚwVm§H$ K Ho$
_mÜ`_ go à{VñWm{nV H$a {X`m OmE, Vmo ZE {d^dmÝVa H$m _mZ __________ hmoJm & 1

12. AY«w{dV àH$me {dab _mÜ`_ go gKZ _mÜ`_ _| J_Z H$aVm h¡ & `{X namd{V©V Am¡a
And{V©V {H$aU| EH$-Xÿgao Ho$ bå~dV² h¢, Vmo namd{V©V àH$me AmnVZ Ho$ Vb Ho$ _______
a¡{IH$V: Y«w{dV hmoVm h¡ & 1

.55/2/3 6

6. In  decay, a 1
(A) neutron converts into a proton emitting antineutrino.
(B) neutron converts into a proton emitting neutrino.
(C) proton converts into a neutron emitting antineutrino.
(D) proton converts into a neutron emitting neutrino.

7. An electron is released from rest in a region of uniform electric and
magnetic fields acting parallel to each other. The electron will 1
(A) move in a straight line.
(B) move in a circle.
(C) remain stationary.
(D) move in a helical path.
8. At equilibrium, in a p-n junction diode the net current is 1
(A) due to diffusion of majority charge carriers.
(B) due to drift of minority charge carriers.
(C) zero as diffusion and drift currents are equal and opposite.
(D) zero as no charge carriers cross the junction.
9. In an n-type semiconductor, the donor energy level lies 1
(A) at the centre of the energy gap.
(B) just below the conduction band.
(C) just above the valance band.
(D) in the conduction band.
10. When two nuclei (A  10) fuse together to form a heavier nucleus, the 1
(A) binding energy per nucleon increases.
(B) binding energy per nucleon decreases.
(C) binding energy per nucleon does not change.
(D) total binding energy decreases.

Note : Fill in the blanks with appropriate answer :

11. The potential difference between two points in vacuum is Vo. If vacuum is
replaced by a medium of dielectric constant K, the new value of potential
difference will be __________ . 1

12. Unpolarised light passes from a rarer into a denser medium. If the
reflected and the refracted rays are mutually perpendicular, the reflected
light is linearly polarised ___________ to the plane of incidence. 1

.55/2/3 7 P.T.O.

13. {~å~ Am¡a A{^Ñí`H$ b|g Ho$ ~rM dm`w Ho$ ñWmZ na CƒVa AndV©Zm§H$ Ho$ {H$gr _mÜ`_
(Vob) H$m Cn`moJ H$aHo$, {H$gr g§`wº$ gyú_Xeu H$s {d^oXZ j_Vm _| __________ H$s Om
gH$Vr h¡ & 1

14. `§J Ho$ {Û{Par à`moJ _| nX} Ho$ {H$gr {~ÝXþ na ì`{VH$aU H$aVr Xmo Va§Jm| Ho$ ~rM nWmÝVa
5
h¡, `hm±  Cn`moJ {H$E JE àH$me H$s Va§JX¡¿`© h¡ & Bg {~ÝXþ na _________ H$mbr
2
q\«$O hmoJr & 1
AWdm
`{X `§J Ho$ {Û{Par à`moJ _| EH$ {Par nyU©V: ~ÝX hmo, Vmo ZE n¡Q>Z© _§o Ho$ÝÐr` C{ƒð> H$m
H$moUr` gmBµO _________ hmoJm & 1

15. gy`m©ñV AWdm gy`m}X` Ho$ g_` gy`© go h_mao ZoÌm| _| __________ dU© H$m àH$s{U©V àH$me
nhþ±MVm h¡ & 1

ZmoQ> : {ZåZ{b{IV Ho$ CÎma Xr{OE :
16. àH$me-{dÚwV² CËgO©Z _| nX ‘Xohbr Amd¥{Îm’ H$s n[a^mfm {b{IE & 1

17. AmaoI _§o Xem©E AZwgma bå~mB© l H$s {H$gr YmVw H$s N>‹S> PQ H$mo, {H$gr Mwå~H$s` joÌ B
_|, H$moUr` doJ  go AnZo _Ü`-{~ÝXþ (O) go JwµOaZo dmbo {H$gr Aj Ho$ n[aV:, Omo Bg n¥ð>
Ho$ Vb Ho$ bå~dV² h¡, Ky{U©V {H$`m J`m h¡ & Bg N>‹S> Ho$ {~ÝXþ O Am¡a Q Ho$ ~rM {dH${gV
{d^dmÝVa Š`m hmoJm ? 1

18. n Hz Amd¥{Îm Ho$ òmoV H$m Cn`moJ H$aZo na {H$gr àË`mdVu Ymam (ac) n[anW _| Ym[aVm C
Ho$ {H$gr g§Ym[aÌ H$s à{V~mYm Š`m hmoVr h¡ ? 1
AWdm
{H$gr loUr AZwZmX LCR n[anW H$s à{V~mYm H$m _mZ Š`m hmoVm h¡ ? 1

19. Xmo àH$me-gwJ«mhr n¥ð>m| H$s Xohbr Amd¥{Îm`m± H«$_e: v1 Am¡a v2 h¢ & O~ BZ XmoZm| n¥ðm| na
Amd¥{Îm v H$m àH$me AmnVZ H$aVm h¡ Am¡a àH$me BboŠQ´>m°Z CËgO©Z hmoVm h¡, Vmo BZ n¥ð>m| go
CËg{O©V àH$m{eH$-BboŠQ´>m°Zm| Ho$ doJm| H$m AZwnmV Š`m hmoJm ? 1

.55/2/3 8

13. The resolving power of a compound microscope can be _________ by using
a medium (oil) of higher refractive index than air between the object and
the objective lens. 1
14. In Young’s double slit experiment, the path difference between two
5
interferencing waves at a point on the screen is ,  being wavelength
2
of the light used. The ___________ dark fringe will lie at this point. 1
OR
If one of the slits in Young’s double slit experiment is fully closed, the
new pattern has __________ central maximum in angular size. 1

15. At sunset or sunrise, the _____________ scattered coloured light from the
sun reaches our eyes. 1
Note : Answer the following :

16. Define the term ‘threshold frequency’ in photoelectric emission. 1

17. A metallic rod PQ of length l is rotated with an angular velocity  in a

magnetic field B about an axis passing through the mid-point O of the
rod and perpendicular to the plane of paper as shown in the figure. What
is the potential difference developed between the points O and Q of the
rod ? 1

18. What is the impedance of a capacitor of capacitance C in an ac circuit
using source of frequency n Hz ? 1
OR
What is the value of impedance of a resonant series LCR circuit ? 1

19. The threshold frequencies of two photosensitive surfaces are v1 and v2,
respectively. What is the ratio of the velocities of the photoelectrons
emitted from these surfaces when light of frequency v is incident on them
and photoemission occurs ? 1

.55/2/3 9 P.T.O.

20. {H$gr AmXe© àoaH$ go àdm{hV Ymam _| n[adV©Z H$s Xa H$mo \$bZ _mZH$a Cg_| ào[aV
{d.dm.~b (emf) Ho$ _mZ Ho$ {dMaU H$mo Xem©Zo Ho$ {bE J«mµ\$ It{ME &$ 1

IÊS> I
21. {ZåZ{b{IV {dÚwV²-Mwå~H$s` Va§Jm| _| go (a) Ý`yZV_ Va§JX¡¿`©, VWm (b) Ý`yZV_ Amd¥{Îm
{H$gH$s h¡ ? BZ XmoZm| Va§Jm| _| go àË`oH$ H$m EH$ Cn`moJ {b{IE &
Adaº$ Va§J|, gyú_ Va§J|, -{H$aU| Am¡a X-{H$aU| 2
22. >H$moB© Ymamdmhr d¥ÎmmH$ma nme {Oggo 5 A Ymam àdm{hV hmo ahr h¡, AnZo Ho$ÝÐ na  mT H$m
Mwå~H$s` joÌ CËnÞ H$aVm h¡ & Bg nme Ho$ Mwå~H$s` AmKyU© H$m _mZ kmV H$s{OE & 2
23. p-n g§{Y S>m`moS> Ho$ V-I A{^bmj{UH$ It{ME & ñnï> H$s{OE {H$ níM{X{eH$
~m`g Ho$ AYrZ Ymam H«$m§{VH$ dmoëQ>Vm VH$ AZwà`wº$ dmoëQ>Vm na bJ^J {Z^©a Š`m| Zht
H$aVr h¡ & 2

24. {H$gr Ymamdmhr MmbH$ _| nX Amdoe dmhH$m| H$s ‘J{VerbVm’ H$s n[a^mfm {b{IE &
{dlmpÝV H$mb Ho$ nXm| _| J{VerbVm Ho$ {bE g§~§Y àmá H$s{OE & 2
AWdm
{H$gr Ymamdmhr MmbH$ _| nX BboŠQ´>m°Zm| Ho$ ‘Andmh doJ’ H$s n[a^mfm {b{IE & Ymam KZËd
Am¡a BboŠQ´>m°Zm| Ho$ Andmh doJ Ho$ ~rM g§~§Y àmá H$s{OE & 2

25. \$moH$g Xÿar 15 cm Ho$ {H$gr CÎmb Xn©U Ho$ gm_Zo H$moB© {~å~ pñWV h¡ & `h Xn©U {~å~
H$s$ gmBµO H$m AmYm à{V{~å~ ~ZmVm h¡ & (a) {~å~ H$s pñW{V, (b) à{V{~å~ H$s àH¥${V
kmV H$s{OE, VWm (c) à{V{~å~ ~ZZm Xem©Zo Ho$ {bE {H$aU AmaoI It{ME & 2

26. (a) {H$gr ao{S>`moEopŠQ>d nXmW© H$s g{H«$`Vm H$m SI _mÌH$ {b{IE &
(b) `{X 15 df© _| {H$gr ao{S>`moEopŠQ>d nXmW© H$s g{H«$`Vm KQ>H$a AnZo Amapå^H$ _mZ
H$s 1 hmo OmVr h¡, Vmo Bg nXmW© H$s AY© Am`w kmV H$s{OE & 2
8
27. (a) {H$gr àË`dVu Ymam (ac) n[anW _| nX ‘AZwZmX H$s VrúUVm’ H$s ì`m»`m H$s{OE &
(b) {H$gr loUr LCR n[anW _§o, VL = VC  VR h¡ & Bg n[anW Ho$ {bE e{º$ JwUm§H$
H$m _mZ {H$VZm h¡ ? 2
AWdm
V = V0 sin t {d.dm.~b (emf) H$m H$moB© àË`dVu Ymam (ac) òmoV Ym[aVm C Ho$ {H$gr
g§Ym[aÌ go g§`mo{OV h¡ & Bg_| àdm{hV Ymam (I) Ho$ {bE ì`§OH$ ì`wËnÞ H$s{OE & (i) V
Am¡a t VWm (ii) I Am¡a t, Ho$ ~rM J«mµ\$ It{ME & 2
.55/2/3 10

20. Draw the graph showing variation of the value of the induced emf as a
function of rate of change of current flowing through an ideal inductor. 1

SECTION B
21. Which of the following electromagnetic waves has (a) minimum
wavelength, and (b) minimum frequency ? Write one use of each of these
two waves.
Infrared waves, Microwaves, -rays and X-rays 2

22. A circular loop carrying a current 5 A, produces a magnetic field of  mT,
at its centre. Find the value of the magnetic moment of the loop. 2
23. Draw V-I characteristics of a p-n junction diode. Explain, why the current
under reverse bias is almost independent of the applied voltage up to the
critical voltage. 2

24. Define the term ‘mobility’ of charge carriers in a current carrying
conductor. Obtain the relation for mobility in terms of relaxation time. 2
OR
Define the term ‘drift velocity’ of electrons in a current carrying
conductor. Obtain the relationship between the current density and the
drift velocity of electrons. 2

25. An object is placed in front of a convex mirror of focal length 15 cm. It
produces an image that is half the size of the object. Find (a) position of
the object, (b) nature of the image, and (c) draw the ray diagram of image
formation. 2
26. (a) Write the SI unit of activity of a radioactive substance.
(b) Find the half-life of a radioactive substance if the activity of the
1
substance drops to of its initial value in 15 years. 2
8
27. (a) Explain the term ‘sharpness of resonance’ in ac circuit.
(b) In a series LCR circuit, VL = VC  VR. What is the value of power
factor for this circuit ? 2
OR
An ac source of emf V = V0 sin t is connected to a capacitor of
capacitance C. Deduce the expression for the current (I) flowing in it. Plot
the graph of (i) V vs. t, and (ii) I vs. t. 2
.55/2/3 11 P.T.O.

IÊS> J
28. 4 F Ho$ {H$gr g§Ym[aÌ H$mo 12 V H$s ~¡Q>ar go Amdo{eV {H$`m J`m h¡ & ~¡Q>ar H$mo hQ>m {X`m
J`m h¡ VWm g§Ym[aÌ H$s n{Å>H$mAm| Ho$ ~rM Ho$ ñWmZ H$mo namd¡ÚwVm§H$ 8 Ho$ {H$gr namd¡ÚwV
nXmW© (ñb¡~) go nyU©V: ^a {X`m J`m h¡ & (a) g§Ym[aÌ _| g§{MV Amdoe, (b) g§Ym[aÌ H$s
n{Å>H$mAm| Ho$ ~rM {d^dmÝVa, Am¡a (c) g§Ym[aÌ _| g§{MV D$Om©, _| hmoZo dmbo n[adV©Z kmV
H$s{OE & 3
AWdm
Xmo N>moQ>o gd©g_ {dÚwV² {ÛY«wd AB VWm CD {OZ_| àË`oH$ H$m {ÛY«wd AmKyU© 
p h¡, AmaoI

_| Xem©E AZwgma, x-Aj H$s Amoa g§Ho$V H$aVo {H$gr ~mø {dÚwV²-joÌ E _| EH$-Xÿgao go
90 Ho$ H$moU na pñWV h¢ & kmV H$s{OE
(a) Bg ì`dñWm H$m {ÛY«wd AmKyU©, Am¡a
(b) Bg na H$m`©aV ZoQ> ~b-AmKyU© H$m n[a_mU Am¡a {Xem & 3

29. {H$gr IJmobr` XÿaXe©H$ Am¡a {H$gr g§`wº$ gyú_Xeu H$s g§aMZm _| Š`m AÝVa hmoVm h¡ ?
{H$gr g§`wº$ gyú_Xeu Ho$ A{^Ñí`H$ Am¡a Zo{ÌH$m H$s \$moH$g Xÿ[a`m± H«$_e: 1·25 cm Am¡a
5·0 cm h¢ & O~ A§{V_ à{V{~å~ {ZH$Q> {~ÝXþ na ~ZVm h¡, Vmo H$moUr` AmdY©Z 30 àmá
H$aZo Ho$ {bE A{^Ñí`H$ Ho$ gmnoj {~å~ H$s pñW{V kmV H$s{OE & 3

30. gm¡a gob H$m Š`m H$m`© h¡ ? g§jon _| BgH$s H$m`©{d{Y H$s ì`m»`m H$s{OE Am¡a BgH$m I-V
A{^bmj{UH$ dH«$ It{ME & 3

31. {H$gr àH$me-gwJ«mhr n¥ð> na Amn{VV àH$me H$s Va§JX¡¿`© H$mo 1 go 2 H$aZo na Cggo
CËg{O©V àH$m{eH$-BboŠQ´>m°Zm| H$s A{YH$V_ J{VO D$Om© XþJwZr hmo OmVr h¡ & 1 Am¡a 2 Ho$
nXm| _| YmVw n¥ð> Ho$ {bE Xohbr Va§JX¡¿`© Am¡a H$m`©\$bZ Ho$ {bE ì`§OH$ ì`wËnÞ H$s{OE & 3

.55/2/3 12

SECTION C

28. A capacitor of 4 F is charged by a battery of 12 V. The battery is
disconnected and a dielectric slab of dielectric constant 8 is inserted in
between the plates of the capacitor to fill the space completely. Find the
change in the (a) charge stored in the capacitor, (b) potential difference
between the plates of the capacitor, and (c) energy stored in the capacitor. 3
OR
Two small identical electric dipoles AB and CD, each of dipole moment

p are kept at an angle of 90 to each other in an external electric field

E pointing along the x-axis as shown in the figure. Find the
(a) dipole moment of the arrangement, and
(b) magnitude and direction of the net torque acting on it. 3

29. What is the difference in the construction of an astronomical telescope
and a compound microscope ? The focal lengths of the objective and
eyepiece of a compound microscope are 1·25 cm and 5·0 cm, respectively.
Find the position of the object relative to the objective in order to obtain
an angular magnification of 30 when the final image is formed at the
near point. 3
30. What is the function of a solar cell ? Briefly explain its working and draw
its I-V characteristic curve. 3
31. The maximum kinetic energy of the photoelectrons emitted is doubled
when the wavelength of light incident on the photosensitive surface
changes from 1 to 2. Deduce expressions for the threshold wavelength
and work function for the metal surface in terms of 1 and 2. 3

.55/2/3 13 P.T.O.

32. AmaoI _| àË`dVu Ymam (ac) òmoV H$s Amd¥{Îm Ho$ gmW {H$gr g§Ym[aÌ Ho$ à{VKmV _§o {dMaU
H$mo J«mµ\$ Ûmam Xem©`m J`m h¡ &

(a) g§Ym[aÌ H$s Ym[aVm kmV H$s{OE &
(b) {H$gr AmXe© àoaH$ H$m 100 Hz Amd¥{Îm na à{VKmV Bg g§Ym[aÌ H$s Cgr Amd¥{Îm
na à{VKmV Ho$ g_mZ h¡ & àoaH$ Ho$ àoaH$Ëd H$m _mZ kmV H$s{OE &
(c) Amd¥{Îm Ho$ gmW Bg àoaH$ Ho$ à{VKmV _| {dMaU H$mo Xem©Zo Ho$ {bE J«mµ\$ It{ME & 3

33. (a) H$jm g§»`m (n) H$mo \$bZ _mZH$a hmBS´>moS>Z na_mUw _| H$jm H$s {ÌÁ`m (rn) H$m
J«mµ\$ It{ME &
(b) {H$gr hmBS´>moO>Z na_mUw _| àW_ CÎmo{OV AdñWm Am¡a {ÛVr` CÎmo{OV AdñWm _|
{H$gr BboŠQ´>m°Z Ûmam EH$ n[aH«$_U nyam H$aZo _§o bJo g_` H$m AZwnmV kmV
H$s{OE & 3

34. (a) ìhrQ>ñQ>moZ goVw Ho$ {bE g§VwbZ Ho$ à{V~ÝY ì`wËnÞ H$s{OE &
(b) {H$gr _rQ>a goVw H$m n[anW AmaoI `h ì`m»`m H$aZo Ho$ {bE It{ME {H$ _rQ>a goVw
{H$g àH$ma ìhrQ>ñQ>moZ goVw na AmYm[aV h¡ & 3

.55/2/3 14

32. The figure shows the graphical variation of the reactance of a capacitor
with frequency of ac source.

(a) Find the capacitance of the capacitor.

(b) An ideal inductor has the same reactance at 100 Hz frequency as
the capacitor has at the same frequency. Find the value of
inductance of the inductor.

(c) Draw the graph showing the variation of the reactance of this
inductor with frequency. 3

33. (a) Draw the graph of radius of orbit (rn) in hydrogen atom as a
function of orbit number (n).

(b) In a hydrogen atom, find the ratio of the time taken by the electron
to complete one revolution in the first excited and in the second
excited states. 3

34. (a) Derive the condition of balance for Wheatstone bridge.

(b) Draw the circuit diagram of a meter bridge to explain how it is
based on Wheatstone bridge. 3

.55/2/3 15 P.T.O.

IÊS> K
35. (a) {H$gr C^`moÎmb b|g Ho$ {bE b|g _oH$a gyÌ ì`wËnÞ H$s{OE &
(b) 10 cm \$moH$g Xÿar Ho$ {H$gr CÎmb b|g go 12 cm Xÿar na, _w»` Aj na, H$moB©
{~ÝXþ{H$V {~å~ pñWV h¡ & b|g Ho$ Xÿgar Amoa 10 cm Xÿar na {H$gr CÎmb Xn©U H$mo
g_mj aIm J`m h¡ & `{X A§{V_ à{V{~å~ {~å~ Ho$ g§nmVr h¡, Vmo {H$aU AmaoI
It{ME Am¡a CÎmb Xn©U H$s \$moH$g Xÿar kmV H$s{OE & 5

AWdm
(a) Va§JmJ« {H$go H$hVo h¢ ? `h {H$g àH$ma àdY©Z H$aVm h¡ & hmBJoÝg Ho$ {gÕmÝV H$m
Cn`moJ H$aHo$ {H$gr n¥ð> go g_Vb Va§JmJ« Ho$ namdV©Z H$s ì`m»`m VWm namdV©Z Ho$
{Z`_m| H$m gË`mnZ H$s{OE &
(b) {H$gr nVbr {Par na 500 nm Va§JX¡¿`© H$m nVbm (g_mÝVa) àH$me nw§O AmnVZ
H$aVm h¡ {OgHo$ \$bñdê$n 1 m Xÿar na pñWV nX} na {ddV©Z n¡Q>Z© àmá hmoVm h¡ &
`{X nhbm {ZpåZð> nX} Ho$ Ho$ÝÐ go 2·5 mm Xÿar na ~ZVm h¡, Vmo (i) {Par H$s
Mm¡‹S>mB©, Am¡a (ii) nX} Ho$ Ho$ÝÐ go nhbo {ÛVr`H$ C{ƒð> H$s Xÿar kmV H$s{OE & 5

36. (a) `h Xem©Zo Ho$ {bE JmCg Ho$ {Z`_ H$m Cn`moJ H$s{OE {H$ {ÌÁ`m R Ho$ EH$g_mZ
Amdo{eV {H$gr Jmobr` Imob Ho$ ~mha Imob Ho$ Ho$ÝÐ go r Xÿar na {ñWV {H$gr {~ÝXw
na {dÚwV²-joÌ H$m _mZ CVZm hr hmoVm h¡, {OVZm {H$ Ho$ÝÐ na gånyU© Amdoe H$mo
gm§{ÐV _mZH$a Bgr {~ÝXþ na hmoVm & Xÿar r Ho$ gmW, r  R Am¡a r  R Ho$ {bE, ZoQ>
{dÚwV²-joÌ Ho$ {dMaU H$mo Xem©Zo Ho$ {bE J«mµ\$ ^r It{ME &
(b) Xmo {~ÝXþ Amdoe + 1 C Am¡a + 4 C EH$-Xÿgao go 30 cm Xÿar na pñWV h¢ &
BZ XmoZm| Amdoem| H$mo {_bmZo dmbr aoIm na + 1 C Amdoe go {H$VZr Xÿar na
{dÚwV²-joÌ eyÝ` hmoJm ? 5
AWdm

(a) {H$gr ~mø EH$g_mZ {dÚwV²-joÌ E _| Xmo {~ÝXþ Amdoe q1 Am¡a q2 EH$-Xÿgao go
r Xÿar na pñWV h¡§ & Amdoem| Ho$ Bg {ZH$m` H$mo g§H${bV H$aZo _| {H$`m J`m H$m`©
kmV H$s{OE &
.55/2/3 16

SECTION D

35. (a) Derive lens maker’s formula for a biconvex lens.

(b) A point object is placed at a distance of 12 cm on the principal axis
of a convex lens of focal length 10 cm. A convex mirror is placed
coaxially on the other side of the lens at a distance of 10 cm. If the
final image coincides with the object, sketch the ray diagram and
find the focal length of the convex mirror. 5

OR

(a) What is a wavefront ? How does it propagate ? Using Huygens’
principle, explain reflection of a plane wavefront from a surface
and verify the laws of reflection.

(b) A parallel beam of light of wavelength 500 nm falls on a narrow
slit and the resulting diffraction pattern is obtained on a screen
1 m away. If the first minimum is formed at a distance of 2·5 mm
from the centre of the screen, find the (i) width of the slit, and
(ii) distance of first secondary maximum from the centre of the
screen. 5

36. (a) Use Gauss’s law to show that due to a uniformly charged spherical
shell of radius R, the electric field at any point situated outside the
shell at a distance r from its centre is equal to the electric field at
the same point, when the entire charge on the shell were
concentrated at its centre. Also plot the graph showing the
variation of electric field with r, for r  R and r  R.

(b) Two point charges of + 1 C and + 4 C are kept 30 cm apart. How
far from the + 1 C charge on the line joining the two charges, will
the net electric field be zero ? 5

OR

(a) Two point charges q1 and q2 are kept r distance apart in a uniform

external electric field E . Find the amount of work done in
assembling this system of charges.
.55/2/3 17 P.T.O.

(b) 20 cm ^wOm H$m H$moB© KZ AmaoI _| Xem©E AZwgma {H$gr joÌ _| aIm h¡ & Bg joÌ

_| H$moB© {dÚwV²-joÌ E Bg àH$ma {dÚ_mZ h¡ {H$ {H$gr {~ÝXþ na {d^d H$mo Bg
àH$ma ì`º$ {H$`m OmVm h¡
V = 10x + 5, Ohm± V dmoëQ _|> VWm x _rQ>a _| h¡ &

kmV H$s{OE

(i) {dÚwV²-joÌ E , Am¡a
(ii) Bg KZ go JwµOaZo dmbm Hw$b {dÚwV² âbŠg & 5

37. (a) {ÌÁ`m R Ho$ {H$gr d¥ÎmmH$ma nme go Ymam I àdm{hV hmo ahr h¡ & Bg nme Ho$ Ho$ÝÐ go
BgHo$ Aj na pñWV x Xÿar Ho$ {H$gr {~ÝXþ na Mwå~H$s` joÌ Ho$ {bE ì`§OH$ àmá
H$s{OE &
(b) 2 m bå~r H$moB© MmbH$ N>‹S> {H$gr j¡{VO _oµO na CÎma-X{jU {Xem _| aIr h¡ &
Bg_§o X{jU go CÎma H$s Amoa 5 A Ymam àdm{hV hmo ahr h¡ & Bg N>‹S> na H$m`©aV
Mwå~H$s` ~b H$s {Xem Am¡a n[a_mU kmV H$s{OE & `h {X`m J`m h¡ {H$ Bg ñWmZ
na n¥Ïdr H$m Mwå~H$s` joÌ 0·6  10–4 T VWm Z{V H$moU  h¡ & 5
6
AWdm
(a) {H$gr EH$g_mZ Mwå~H$s` joÌ _| {H$gr J¡ëdoZmo_rQ>a H$s Ymamdmhr Am`VmH$ma
Hw$ÊS>br na H$m`©aV {djonH$ ~b-AmKyU© Ho$ {bE ì`§OH$ àmá H$s{OE & Mb
Hw$ÊS>br J¡ëdoZmo_rQ>a _| Aar` Mwå~H$s` joÌ H$m Cn`moJ Š`m| {H$`m OmVm h¡ ?
(b) {H$gr gmBŠbmoQ´>m°Z, {OgH$s S>rµO H$s {ÌÁ`m 40 cm h¡, Ho$ Ûmam Ðì`_mZ
1·6  10–27 kg Am¡a Amdoe 1·6  10–19 C Ho$ H$Um| H$mo Ëd[aV {H$`m J`m h¡ &
Bg_| 0·4 T Ho$ Mwå~H$s` joÌ H$m Cn`moJ {H$`m J`m h¡ & Bg ËdaH$ Ûmam H$U -nw§O
H$mo Xr J`r J{VO D$Om© (MeV _|) kmV H$s{OE & 5

.55/2/3 18

(b) A cube of side 20 cm is kept in a region as shown in the figure. An

electric field E exists in the region such that the potential at a
point is given by V = 10x + 5, where V is in volt and x is in m.

Find the

(i) electric field E , and
(ii) total electric flux through the cube. 5

37. (a) A circular loop of radius R carries a current I. Obtain an
expression for the magnetic field at a point on its axis at a distance
x from its centre.
(b) A conducting rod of length 2 m is placed on a horizontal table in
north-south direction. It carries a current of 5 A from south to
north. Find the direction and magnitude of the magnetic force
acting on the rod. Given that the Earth’s magnetic field at the

place is 0·6  10–4 T and angle of dip is . 5
6
OR
(a) Obtain the expression for the deflecting torque acting on the
current carrying rectangular coil of a galvanometer in a uniform
magnetic field. Why is a radial magnetic field employed in the
moving coil galvanometer ?
(b) Particles of mass 1·6  10–27 kg and charge 1·6  10–19 C are
accelerated in a cyclotron of dee radius 40 cm. It employs a
magnetic field 0·4 T. Find the kinetic energy (in MeV) of the
particle beam imparted by the accelerator. 5

.55/2/3 19 P.T.O.