CBSE Class 12 Physics Question Paper 2020 Set 55-3-1

H$moS> Z§.
Code No. 55/3/1
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

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

gm_mÝ` {ZX}e :
{ZåZ{b{IV {ZX}em| H$mo ~hþV gmdYmZr go n{‹T>E Am¡a CZH$m g™Vr go nmbZ H$s{OE :
(i) `h àíZ-nÌ Mma IÊS>m| _§| {d^m{OV {H$`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` àH$ma Ho$ 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` àH$ma Ho$ 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$m| dmbo$ 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) Ho$ëHw$boQ>am| AWdm bm°J Q>o~bm| 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
.55/3/1 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 one mark each.
(iv) Section B – Questions no. 21 to 27 are short answer type questions,
carrying two marks each.
(v) Section C – Questions no. 28 to 34 are long answer type questions,
carrying three marks each.
(vi) Section D – Questions no. 35 to 37 are also long answer type questions,
carrying five 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
.55/3/1 3 P.T.O.

IÊS> H$
ZmoQ> : ZrMo {XE JE àË`oH$ àíZ H$m g~go A{YH$ Cn`wº$ {dH$ën Mw{ZE :
1. `{X {H$gr YZmdoe H$mo {Og {dÚwV²-joÌ _| dh pñWV h¡, CgHo$ {déÕ {dñWm{nV {H$`m OmE,
Vmo 1
(A) Cg Amdoe na {dÚwV²-joÌ Ûmam H$m`© {H$`m OmEJm &
(B) {dÚwV²-joÌ H$s Vrd«Vm H$_ hmo OmEJr &
(C) {ZH$m` H$s D$Om© H$_ hmo OmEJr &
(D) Amdoe H$mo ñWmZmÝV[aV ({dñWm{nV) H$aZo dmbo ~mø òmoV Ûmam D$Om© àXmZ H$s
OmEJr &
2. 1 C Amdoe go {ZJ©V {dÚwV² âbŠg hmoVm h¡ 1
1
(A)
0

(B) 4
4
(C)
0

(D) 0

3. C1 Am¡a C2 Ym[aVmAm| Ho$ Xmo g§Ym[aÌm| H$mo nmíd© _| g§`mo{OV {H$`m J`m h¡ & `{X Bg
g§`moOZ H$mo H$moB© Amdoe Q {X`m OmE, Vmo g§Ym[aÌm| C1 Am¡a C2 na Amdoem| H$m AZwnmV
hmoJm 1

C1
(A)
C2

C1
(B)
C2

C2
(C)
C1

C2
(D)
C1

.55/3/1 4

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

1. If a positive charge is displaced against the electric field in which it was
situated, then 1
(A) work will be done by the electric field on the charge.
(B) the intensity of the electric field decreases.
(C) energy of the system will decrease.
(D) energy will be provided by external source displacing the charge.

2. The electric flux emerging out from 1 C charge is 1

1
(A)
0

(B) 4

4
(C)
0

(D) 0

3. Two capacitors of capacitances C1 and C2 are connected in parallel. If a
charge Q is given to the combination, the ratio of the charge on the
capacitor C1 to the charge on C2 will be 1

C1
(A)
C2

C1
(B)
C2

C2
(C)
C1

C2
(D)
C1

.55/3/1 5 P.T.O.

4. {H$gr MmbH$ H$m {dÚwV² à{VamoY Cg MmbH$ Ho$/H$s 1

(A) AZwàñW-H$mQ> joÌ\$b Ho$ AZwH«$_mZwnmV _| {dMaU H$aVm h¡ &
(B) Vmn _| d¥{Õ hmoZo na KQ>Vm h¡ &
(C) MmbH$Vm _| d¥{Ó hmoZo na KQ>Vm h¡ &
(D) AmH¥${V na {Z^©a Zht H$aVm naÝVw Ho$db CgHo$ Am`VZ na {Z^©a H$aVm h¡ &

5. m2V–1s–1 {ZåZ{b{IV _| go {H$gH$m SI _mÌH$ h¡ ? 1

(A) Andmh doJ
(B) J{VerbVm
(C) à{VamoYH$Vm
(D) {d^d àdUVm

6. {H$gr hrQ>a Ho$ Ad`d (E{b_oÝQ>) H$m AZw_Vm§H$ (P, V) h¡ & `{X Bgo V dmoëQ>Vm Ho$ òmoV
2
Ho$ {gam| go g§`mo{OV {H$`m OmE, Vmo BgHo$ Ûmam Cn^wº$ e{º$ hmoJr 1
(A) P
(B) 2P
P
(C)
2
P
(D)
4

7. hmBS´>moOZ na_mUw Ho$ ~moa _m°S>b _|, ndt {d{dº$ H$jm _§o BboŠQ´>m°Z H$s Hw$b D$Om©
{ZåZ{b{IV _| go {H$gHo$ AZwH«$_mZwnmVr hmoVr h¡ ? 1
(A) n
1
(B)
n
(C) n2
1
(D)
n2

.55/3/1 6

4. The electrical resistance of a conductor 1
(A) varies directly proportional to its area of cross-section.
(B) decreases with increase in its temperature.
(C) decreases with increase in its conductivity.
(D) is independent of its shape but depends only on its volume.

5. m2V–1s–1 is the SI unit of which of the following ? 1
(A) Drift velocity
(B) Mobility
(C) Resistivity
(D) Potential gradient

6. The element of a heater is rated (P, V). If it is connected across a source
V
of voltage , then the power consumed by it will be 1
2
(A) P
(B) 2P
P
(C)
2
P
(D)
4

7. In Bohr’s model of hydrogen atom, the total energy of the electron in
nth discrete orbit is proportional to 1
(A) n
1
(B)
n
(C) n2
1
(D)
n2

.55/3/1 7 P.T.O.

8. {H$gr µOoZa S>m`moS> _§o 1
(A) p-\$bH$ AË`{YH$ An{_{lV VWm n-\$bH$ Aën An{_{lV hmoVm h¡ &
(B) n-\$bH$ AË`{YH$ An{_{lV VWm p-\$bH$ Aën An{_{lV hmoVm h¡ &
(C) n-\$bH$ Am¡a p-\$bH$ XmoZm| hr AË`{YH$ An{_{lV hmoVo h¢ &
(D) n-\$bH$ Am¡a p-\$bH$ XmoZm| hr Aën An{_{lV hmoVo h¢ &

9. {H$gr joÌ _| Mwå~H$s` joÌ EH$g_mZ h¡ & H$moB© àmoQ>m°Z Bg joÌ _| {H$gr doJ go Mwå~H$s`
joÌ H$s {Xem go 45 H$m H$moU ~ZmVo hþE àdoe H$aVm h¡ & Bg joÌ _| `h àmoQ>m°Z {Og nW
na J{V H$aoJm, CgH$s AmH¥${V hmoJr 1
(A) gab aoIm
(B) d¥Îm
(C) g{n©b
(D) Hw$ÊS>{bZr

10. H$moB© Ymamdmhr g_{Û~mhþ g_H$mo{UH$ nme PQR {H$gr EH$g_mZ Mwå~H$s` joÌ B , Omo
PR Ho$ AZw{Xe g§Ho$V H$aVm h¡, _| pñWV h¡ & `{X ^wOm PQ na H$m`©aV Mwå~H$s` ~b F
h¡, Vmo ^wOm QR na H$m`©aV Mwå~H$s` ~b hmoJm 1

(A) F
F
(B)
2

(C) 2F
(D) –F

.55/3/1 8

8. A zener diode has 1
(A) heavily doped p-side and lightly doped n-side.
(B) heavily doped n-side and lightly doped p-side.
(C) heavily doped n-side as well as p-side.
(D) lightly doped n-side as well as p-side.

9. A region has a uniform magnetic field in it. A proton enters into the
region with velocity making an angle of 45 with the direction of the
magnetic field. In this region the proton will move on a path having the
shape of a 1
(A) straight line
(B) circle
(C) spiral
(D) helix

10. An isosceles right angled current carrying loop PQR is placed in a

uniform magnetic field B pointing along PR. If the magnetic force acting
on the arm PQ is F, then the magnetic force which acts on the arm QR
will be 1

(A) F

F
(B)
2

(C) 2F

(D) –F

.55/3/1 9 P.T.O.

ZmoQ> : Cn`wº$ CÎma go [aº$ ñWmZm| H$mo ^[aE :
11. {H$gr aoIm òmoV go CËnÞ Va§JmJ« H$s AmH¥${V ___________ hmoVr h¡ & 1
12. {H$gr A{^gmar b|g Ho$ nXmW© H$m AndV©Zm§H$ 1·5 h¡ & `{X dm`w H$mo AndV©Zm§H$ 1·6 Ho$
{H$gr AÝ` _mÜ`_ go à{VñWm{nV H$a {X`m OmE, Vmo `h b|g ___________ b|g H$s
^m±{V ì`dhma H$aoJm & 1
13. `§J Ho$ {Û{Par à`moJ _|, Xmo {P[a`m| Ho$ ~rM n¥WH$Z H$mo AmYm H$a {X`m J`m h¡ & Z`r q\«$O
Mm¡‹S>mB© H$m _mZ àmapå^H$ _mZ H$m ___________ JwZm hmo OmEJm & 1

14. dm`w-H$m±M AÝVamn¥ð> Ho$ {bE ~w«wñQ>a H$moU H$m _mZ  h¡, AV: H$m±M H$m AndV©Zm§H$
3
___________ h¡ & 1
15. àH$me-{dÚwV² à^md _|, CËg{O©V àH$m{eH$-BboŠQ´>m°Zm| H$s g§»`m Amn{VV àH$me Ho$/H$s
___________ Ho$ AZwH«$_mZwnmVr hmoVr h¡ & 1
AWdm
Xohbr Amd¥{Îm v0 (v > v0) Ho$ {H$gr àH$me-gwJ«mhr n¥ð> na Amd¥{Îm v H$m àH$me AmnVZ
H$aVm h¡ & CËg{O©V àH$m{eH$-BboŠQ´>m°Zm| H$s J{VO D$Om© H$m _mZ ___________ hmoJm & 1

ZmoQ> : {ZåZ{b{IV Ho$ CÎma Xr{OE :
16. {H$gr LCR loUr n[anW go àË`mdVu Ymam (ac) àdm{hV hmo ahr h¡ & AZwZmX H$s pñW{V _§o
n[anW H$s à{V~mYm Š`m hmoJr ? 1

17. {H$gr ~mø Mwå~H$s` joÌ _| Xmo gd©g_ Hw$ÊS>{b`m±, {OZ_| EH$ H$m°na VWm Xÿgar Eobw{_{Z`_
H$s h¡, g_mZ H$moUr` Mmb go KyU©Z H$a ahr h¢ & BZ XmoZm| _| go {H$g Hw$ÊS>br _| ào[aV Ymam
A{YH$ hmoJr ? 1

18. {H$gr àË`mdVu Ymam (ac) n[anW _|, AZwà`wº$ dmoëQ>Vm Am¡a àdm{hV Ymam H«$_e:

E = E0 sin t Am¡a I = I0 sin (t + ) h¢ & Bg n[anW _| EH$ MH«$ _| Am¡gV Cn^wº$
2
e{º$ Š`m hmoJr ? 1
AWdm
Š`m hmoVm h¡ O~ {H$gr YmVw Ho$ JwQ>Ho$ H$mo {H$gr n[adVu Mwå~H$s` joÌ _§o aIm OmVm h¡ ? 1

19. {dÚwV²-Mwå~H$s` Va§Jm| H$mo CËnÞ H$aZo _| ^maVr` ^m¡{VH$s {dkmZr Oo.gr. ~mog Ho$ `moJXmZ
H$m C„oI H$s{OE & 1

20. 1016 Hz go 1020 Hz Amd¥{Îm n[aga H$s {dÚwV²-Mwå~H$s` Va§Jm| H$m EH$ Cn`moJ {b{IE & 1

.55/3/1 10

Note : Fill in the blanks with appropriate answer :
11. The shape of the wavefront originating from a line source is __________ . 1
12. The refractive index of the material of a converging lens is 1·5. If air is
replaced by a medium of refractive index 1·6, then the lens will now
behave as a __________ lens. 1
13. In Young’s double slit experiment, the separation between the two slits is
halved. The new fringe width will be __________ times its initial value. 1

14. The value of Brewster’s angle for air-glass interface is , hence the
3
refractive index of glass is __________ . 1
15. In photoelectric effect, the number of emitted photoelectrons is
proportional to __________ of incident light. 1
OR
Light of frequency v is incident on a photosensitive surface of threshold
frequency v0 (v > v0). The value of kinetic energy of the emitted
photoelectrons will be __________ . 1

Note : Answer the following :

16. An ac is passed through a series LCR circuit. What is the impedance of
the circuit at resonance ? 1

17. Two identical coils, one of copper and the other of aluminium are rotated
with the same angular speed in an external magnetic field. In which of
the two coils will the induced current be more ? 1
18. In an ac circuit, the applied voltage and flowing current are E = E0 sin t

and I = I0 sin (t + ) respectively. What is the average power consumed
2
in one cycle in this circuit ? 1
OR
What happens when a block of metal is kept in a varying magnetic field ? 1
19. Mention the contribution of Indian physicist J.C. Bose in the production
of electromagnetic waves. 1

20. Write one use of the electromagnetic waves of frequency range from
1016 Hz to 1020 Hz. 1

.55/3/1 11 P.T.O.

IÊS> I
21. Xmo gob {OZHo$ {d.dm. ~b (emf) E1 Am¡a E2 (E1 > E2) h¢, ZrMo AmaoI _| Xem©E AZwgma
g§`mo{OV h¢ & O~ {~ÝXþAm| A Am¡a B Ho$ ~rM {d^dmÝVa _mnZo Ho$ {bE, BÝh| {H$gr
nmoQ>¡pÝe`mo_rQ>a go g§`mo{OV {H$`m OmVm h¡, Vmo nmoQ>¡pÝe`mo_rQ>a Ho$ Vma na g§VwbZ bå~mB©
300 cm hmoVr h¡ & naÝVw `hr nmoQ>¡pÝe`mo_rQ>>a {~ÝXþAm| A Am¡a C Ho$ ~rM {d^dmÝVa Ho$ {bE

g§VwbZ bå~mB© 100 cm XoVm h¡ & E1 kmV H$s{OE & 2
E2

22. Xmo gd©g_ N>‹S>|, {OZ_| EH$ AZwMwå~H$s` nXmW© H$s VWm Xÿgar à{VMwå~H$s` nXmW© H$s ~Zr
h¡, {H$gr ~mø EH$g_mZ Mwå~H$s` joÌ _| joÌ Ho$ g_mÝVa aIr OmVr h¢ & àË`oH$ àH$aU _|
Mwå~H$s` joÌ Ho$ n¡Q>Z© _| hmoZo dmbo ê$nmÝVaUm| H$mo AmaoI ItMH$a Xem©BE & 2
23. Xmo g_Vbr` Am¡a g§Ho$ÝÐr Hw$ÊS>{b`m| 1 Am¡a 2 _o| \o$am| H$s g§»`m H«$_e: N1 Am¡a N2 h¡
VWm BZH$s {ÌÁ`mE± r1 Am¡a r2 (r2 >> r1) h¢ & Bg {ZH$m` Ho$ AÝ`moÝ` àoaH$Ëd Ho$ {bE
ì`§OH$ ì`wËnÞ H$s{OE & 2
24. H$moB© Xmobm`_mZ Amdoe {H$g àH$ma {dÚwV²-Mwå~H$s` Va§J {d{H${aV H$aVm h¡ ? Xmobm`_mZ
Amdoe H$s Amd¥{Îm VWm {d{H$[aV Va§J H$s Amd¥{Îm Ho$ ~rM g§~§Y Xr{OE & 2
AWdm
(a) Bg VÏ` H$s g§jon _| ì`m»`m H$s{OE {H$ {dÚwV²-Mwå~H$s` Va§J| D$Om© dhZ H$aVr h¢ &
(b) h_ gy`© H$s {H$aUm| (Yyn) Ho$ H$maU Xm~ H$m AZw^d Š`m| Zht H$aVo h¢ ? 2
25. f1 \$moH$g Xÿar H$m H$moB© A{^gmar b|g f2 \$moH$g Xÿar (f1 > f2) Ho$ {H$gr Angmar b|g Ho$
g_mj gånH©$ _| aIm J`m h¡ & f1 Am¡a f2 Ho$ nXm| _| Bg g§`moOZ H$s j_Vm Am¡a àH¥${V
{ZYm©[aV H$s{OE & 2
AWdm
{H$gr g§`wº$ gyú_Xeu H$s {d^oXZ j_Vm {H$g àH$ma à^m{dV hmoVr h¡ `{X
(a) Cn`moJ {H$E JE àH$me H$s Va§JX¡¿`© H$_ hmo OmVr h¡ , Am¡a (b) BgHo$ A{^Ñí`H$ b|g
H$m ì`mg A{YH$ hmo OmVm h¡ ? AnZo CÎmam| H$s nw{ï> H$s{OE & 2
26. nXm| (a) Xohbr Amd¥{Îm, Am¡a (b) {ZamoYr {d^d H$s n[a^mfm Xr{OE & AmB§ñQ>mBZ H$s
àH$me-{dÚwV² g_rH$aU _| BZ nXm| H$mo {H$g àH$ma g_m{dï> {H$`m J`m h¡ ? 2
27. H$moB© hmBS´>moOZ na_mUw AnZr V¥Vr` CÎmoOH$ AdñWm _| h¡ &
(a) {ZåZV_ AdñWm _§o AmZo go nyd© Bggo {H$VZr ñnoŠQ´>_r aoImE± CËg{O©V H$s Om gH$Vr
h¢ ? BZ g§H«$_Um| H$mo D$Om© ñVa AmaoI _| Xem©BE &
(b) Cn`w©º$ g§H«$_Um| _§o go {H$g_| g~go N>moQ>r Va§JX¡¿`© H$s ñnoŠQ´>_r aoIm CËg{O©V hmoJr ? 2

.55/3/1 12

SECTION B
21. Two cells of emf E1 and E2 (E1 > E2) are connected as shown in the figure
below. When a potentiometer is used to measure potential difference
between the points A and B, the balancing length of the potentiometer
wire is 300 cm. But the same potentiometer for the potential difference
E
between points A and C, gives the balancing length 100 cm. Find 1 . 2
E2

22. Two identical bars, one of paramagnetic material and other of
diamagnetic material are kept in a uniform external magnetic field
parallel to it. Draw diagrammatically the modifications in the magnetic
field pattern in each case. 2
23. Two coplanar and concentric coils 1 and 2 have respectively the number
of turns N1 and N2 and radii r1 and r2 (r2 >> r1). Deduce the expression
for mutual inductance of this system. 2
24. How does an oscillating charge radiate an electromagnetic wave ? Give
the relation between the frequency of radiated wave and the frequency of
oscillating charge. 2
OR
(a) Explain briefly the fact that electromagnetic waves carry energy.
(b) Why do we not feel the pressure due to sunshine ? 2
25. A converging lens of focal length f1 is placed coaxially in contact with a
diverging lens of focal length f2 (f1 > f2). Determine the power and nature
of the combination in terms of f1 and f2. 2
OR
How is the resolving power of a compound microscope affected if
(a) wavelength of light used is decreased, and (b) the diameter of its
objective lens is increased ? Justify your answers. 2
26. Define the terms (a) threshold frequency, and (b) stopping potential. How
were these terms incorporated in Einstein’s photoelectric equation ? 2
27. A hydrogen atom is in its third excited state.
(a) How many spectral lines can be emitted by it before coming to the
ground state ? Show these transitions in the energy level diagram.
(b) In which of the above transitions will the spectral line of shortest
wavelength be emitted ? 2
.55/3/1 13 P.T.O.

IÊS> J

28. (a) {H$gr {dÚwV² MmbH$ _o| BboŠQ´>m°Zm| Ho$ `mÑpÀN>H$ doJ Am¡a Andmh doJ Ho$ ~rM
{d^oXZ H$s{OE & BZH$s n[a_mUm| H$s H$mo{Q> Xr{OE &
(b) EH$g_mZ AZwàñW-H$mQ joÌ\$b H$m H$moB© MmbH$ {H$gr n[adVu dc dmoëQ>Vm òmoV Ho$
{gam| go g§`mo{OV h¡ & BgHo$ {bE Ymam KZËd (J) Ho$ \$bZ Ho$ ê$n _§o BboŠQ´>m°Zm| Ho$
Andmh doJ (vd) Ho$ {dMaU H$mo Xem©Zo Ho$ {bE J«m\$ It{ME & 3

29. {H$gr loUr LCR àË`mdVu Ymam (ac) n[anW _| L = 2·0 H, C = 32 F VWm R = 10 
h¡ &
(a) àË`mdVu Ymam (ac) H$s {H$g H$moUr` Amd¥{Îm na `h AZwZmX H$aoJm ?
(b) Bg n[anW H$m Q _mZ n[aH${bV H$s{OE & 3
AWdm
5
H àoaH$Ëd H$m H$moB© AmXe© àoaH$ 200 V, 50 Hz H$s àË`mdVu Ymam (ac) Amny{V© go

g§`mo{OV h¡ &
(a) Bg àoaH$ _| Ymam H$m dJ©-_mÜ`-_yb (rms) Am¡a {eIa _mZ n[aH${bV H$s{OE &
(b) àoaH$ go àdm{hV Ymam Am¡a AZwà`wº$ dmoëQ>Vm Ho$ ~rM H$bmÝVa Š`m h¡ ? `{X n[anW
_| Bg àoaH$ Ho$ gmW loUr _| H$moB© N>moQ>m à{VamoY g§`mo{OV H$a {X`m OmE, Vmo
H$bmÝVa _§o Š`m n[adV©Z hmoJm ? 3

30. (a) Amdí`H$ {H$aU AmaoI H$m Cn`moJ H$aHo$ AdVb Xn©U Ho$ {bE Xn©U gyÌ ì`wËnÞ
H$s{OE &
(b) {H$gr AdVb Xn©U Ho$ _w»` Aj Ho$ AZw{Xe pñWV {H$gr _mnH$ n¡_mZo ({OgHo$
A§emH$Z g_XÿañW h¢) Ho$ {dd{Y©V à{V{~å~ _| A§emH$Z g_XÿañW Zht hmoVo &
ì`m»`m H$s{OE & 3

31. (a) {H$gr nXmW© Ho$ ^m¡{VH$ KZËd H$s VwbZm _| CgHo$ Zm{^H$s` nXmW© H$m KZËd
~hþV-~hþV A{YH$ hmoVm h¡ & ì`m»`m H$s{OE &
(b) Zm{^H$s` ~b Ý`ypŠbAm°Zm| Ho$ ~rM Hy$bm°_r ~b Zht hmoVo & ì`m»`m H$s{OE &
(c) {H$gr Zm{^H$ Ho$ ^rVa Ý`ypŠbAm°Zm| Ho$ ~rM H$s Xÿar H$mo \$bZ _mZH$a Ý`ypŠbAm°Zm|
Ho$ {H$gr `wJb Ho$ ~rM pñW{VO D$Om© H$m J«m\$ It{ME & 3
.55/3/1 14

SECTION C

28. (a) Differentiate between the random velocity and the drift velocity of
electrons in an electrical conductor. Give their order of
magnitudes.

(b) A conductor of uniform cross-sectional area is connected across a
dc source of variable voltage. Draw a graph showing variation of
drift velocity of electrons (vd) as a function of current density (J)
in it. 3

29. A series LCR ac circuit has L = 2·0 H, C = 32 F and R = 10 .
(a) At what angular frequency of ac will it resonate ?
(b) Calculate the Q value of the circuit. 3
OR
5
An ideal inductor of H inductance is connected to a 200 V, 50 Hz ac

supply.
(a) Calculate the rms and peak value of current in the inductor.
(b) What is the phase difference between current through the inductor
and the applied voltage ? How will it change if a small resistance is
connected in series with this inductor in the circuit ? 3

30. (a) Using the necessary ray diagram, derive the mirror formula for a
concave mirror.
(b) In the magnified image of a measuring scale (with equidistant
markings) lying along the principal axis of a concave mirror, the
markings are not equidistant. Explain. 3

31. (a) The density of the nuclear matter is tremendously larger than the
physical density of the material. Explain.
(b) The nuclear forces are not coulomb forces between nucleons.
Explain.
(c) Draw a plot of the potential energy between a pair of nucleons as a
function of distance between them inside a nucleus. 3
.55/3/1 15 P.T.O.

32. {H$gr BboŠQ´>m°Z H$s Va§J àH¥${V go AmnH$m Š`m A{^àm` h¡ ? Xo ~«m°½br A{^J¥hrV/n[aH$ënZm
Ûmam hmBS´>moOZ na_mUw Ho$ ~moa _m°S>b _| H$jm _§o n[aH«$_m H$aVo hþE BboŠQ´>m°Z Ho$ H$moUr` g§doJ
Ho$ ŠdmÝQ>_rH$aU H$s ì`m»`m {H$g àH$ma H$s JB© ? 3

33. Cg S>m`moS> H$m Zm_ {b{IE Omo dmoëQ>Vm {Z`§ÌH$ Ho$ ê$n _| H$m`© H$a gH$Vm h¡ & Zm_m§{H$V
n[anW AmaoI H$s ghm`Vm go BgH$s H$m`©{d{Y H$s ì`m»`m H$s{OE & BgH$m V – I
A{^bmj{UH$ It{ME & 3

34. (a) {H$gr Z¡O AY©MmbH$ H$mo OmZ~yP H$a Cg_| AewÕ na_mUwAm| H$mo {_bmH$a ~mø
AY©MmbH$ _| Š`m| n[ad{V©V {H$`m OmVm h¡ ?
(b) {H$gr {d^d amo{YH$m H$m g¥OZ H$aZo Ho$ {bE p-n g§{Y joÌ _| hmoZo dmbr Xmo
à{H«$`mAm| H$s g§jon _| ì`m»`m H$s{OE & 3

IÊS> K
 
35. (a) {ÛY«wd AmKyU© p Ho$ {H$gr {dÚwV² {ÛY«wd H$mo {H$gr EH$g_mZ {dÚwV²-joÌ E _| 
H$moU ~ZmVo hþE aIm J`m h¡ & Bg na H$m`©aV ~b-AmKyU© (   ) Ho$ {bE ì`§OH$
ì`wËnÞ H$s{OE & {dÚwV²-joÌ Ho$ gmnoj {ÛY«wd H$m dh {dÝ`mg kmV H$s{OE {Og_|
Cg na ~b-AmKyU© (i) A{YH$V_, Am¡a (ii) A{YH$V_ H$m AmYm h¡ &
(b) Xmo {~ÝXþ Amdoe q1 = + 1 C Am¡a q2 = + 4 C dm`w _| EH$-Xÿgao go 2 m Xÿar na
pñWV h¢ & BZ XmoZm| Amdoem| H$mo {_bmZo dmbr aoIm Ho$ AZw{Xe q1 go {H$g Xÿar na
XmoZm| Amdoem| Ho$ H$maU ZoQ> {dÚwV²-joÌ eyÝ` hmoJm ? 5

AWdm
(a) {H$gr g_mÝVa n{Å>H$m g§Ym[aÌ, {OgH$s Ym[aVm C Am¡a {Ogo dmoëQ>Vm V VH$
Amdo{eV {H$`m J`m h¡, _| g§{MV D$Om© Ho$ {bE ì`§OH$ ì`wËnÞ H$s{OE & g§Ym[aÌ _|
`h D$Om© {H$g àH$ma g§{MV hmoVr h¡ ?
(b) 1 F Ym[aVm Ho$ {H$gr g§Ym[aÌ H$mo CnojUr` AmÝV[aH$ à{VamoY VWm 10 V {d.dm.
~b (emf) H$s {H$gr ~¡Q>ar Ho$ {gam| go g§`mo{OV H$a Amdo{eV {H$`m J`m h¡ & Bg
g§Ym[aÌ H$mo nyU© ê$n go Amdo{eV H$aZo _| ~¡Q>ar Ûmam AmnyV© {H$E JE Amdoe H$s _mÌm
H$m n[aH$bZ H$s{OE & 5

.55/3/1 16

32. What do you mean by wave nature of an electron ? How was quantisation
of angular momentum of the orbiting electron in Bohr’s model of
hydrogen atom explained by de Broglie hypothesis ? 3

33. Name the diode which can act as a voltage regulator. Explain its
working with the help of its labelled circuit diagram. Draw its V – I
characteristic. 3

34. (a) Why is an intrinsic semiconductor deliberately converted into an
extrinsic semiconductor by adding impurity atoms ?
(b) Explain briefly the two processes that occur in p-n junction region
to create a potential barrier. 3

SECTION D


35. (a) An electric dipole of dipole moment p is placed in a uniform

electric field E at an angle  with it. Derive the expression for

torque (  ) acting on it. Find the orientation of the dipole relative
to the electric field for which torque on it is (i) maximum, and
(ii) half of maximum.

(b) Two point charges q1 = + 1 C and q2 = + 4 C are placed 2 m
apart in air. At what distance from q1 along the line joining the
two charges, will the net electric field be zero ? 5

OR

(a) Derive an expression for the energy stored in a parallel plate
capacitor of capacitance C when charged up to voltage V. How is
this energy stored in the capacitor ?

(b) A capacitor of capacitance 1 F is charged by connecting a battery
of negligible internal resistance and emf 10 V across it. Calculate
the amount of charge supplied by the battery in charging the
capacitor fully. 5

.55/3/1 17 P.T.O.

36. (a) Xmo Ymamdmhr bå~o grYo g_mÝVa MmbH$m| Ho$ ~rM à{V EH$m§H$ bå~mB© na H$m`©aV ~b
Ho$ {bE ì`§OH$ ì`wËnÞ H$s{OE & Bg àH$ma EH$ Eopån`a H$s n[a^mfm {b{IE &
(b) Xmo grYo bå~o g_mÝVa MmbH$ dm`w _| EH$-Xÿgao go 12 cm Xÿar na aIo h¢ & XmoZm|
Vmam| go 3 A Ymam àdm{hV hmo ahr h¡ & AmaoI ItMH$a `h Xem©Vo hþE {H$ XmoZm| Vmam|
go àdm{hV YmamAm| H$s {Xem {dnarV h¡, BZ Vmam| Ho$ _Ü` _| {H$gr {~ÝXþ na
Mwå~H$s` joÌ H$m n[a_mU Am¡a {Xem kmV H$s{OE & 5

AWdm
(a) gmBŠbmoQ´>m°Z H$m ì`dñWm AmaoI It{ME & {H$gr Amdo{eV H$U Ho$ Cg nW H$s
AmH¥${V H$s ì`m»`m H$s{OE {Og na dh V~ J{V H$aVm h¡ O~ Cgo gmBŠbmoQ´>m°Z
Ûmam Ëd[aV {H$`m OmVm h¡ &
(b) {H$gr {XE JE J¡ëdoZmo_rQ>a H$mo 2 V, V Am¡a V dmoëQ> n[agam| Ho$ dmoëQ>_rQ>a _|
2
n[ad{V©V H$aZo Ho$ {bE Bg J¡ëdoZmo_rQ>a Ho$ gmW loUr _| g§`mo{OV H«$_e: R1, R2
Am¡a R3 Amo_ Ho$ à{VamoYm| H$s Amdí`H$Vm hmoVr h¡ & R1, R2 Am¡a R3 Ho$ ~rM
g§~§Y àmá H$s{OE & 5

37. (a) g_Vb Y«w{dV àH$me go Š`m VmËn`© h¡ ? AndV©Zm§H$  Ho$ H$m±M Ho$ n¥ð> na H$moU 
~ZmVo hþE H$moB© AY«w{dV àH$me AmnVZ H$aVm h¡ & `{X namd{V©V Am¡a And{V©V
{H$aU| EH$-Xÿgao Ho$ bå~dV² h¢, Vmo  Am¡a  Ho$ ~rM g§~§Y àmá H$s{OE &
(b) Xmo nmoboam°BS>m| P1 Am¡a P2 H$mo H«$m°{gV pñW{V _| aIm J`m h¡ & Vrd«Vm I0 H$m
AY«w{dV àH$me P1 na AmnVZ H$aVm h¡ & `{X P1 H$mo pñWa aIVo hþE P2
H$mo àH$me Ho$ g§MaU H$s {Xem Ho$ n[aV…  H$moU na Ky{U©V {H$`m OmE, Vmo
0 <  < 360 Ho$ {bE Cg àH$me H$s Vrd«Vm Ho$ {bE J«m\$ It{ME Omo (i) P1 Ûmam
nmaJ{_V, VWm (ii) P2 Ûmam nmaJ{_V hmoVm h¡ & 5

AWdm
(a) àH$me Ho$ ì`{VH$aU Ho$ `§J Ho$ {Û-{Par à`moJ H$m g§jon _| dU©Z H$s{OE & Bg n¡Q>Z©
_| q\«$O Mm¡‹S>mB© Ho$ {bE ì`§OH$ ì`wËnÞ H$s{OE &
(b) dm`w go Ob _| AÝVamn¥ð> na Va§JX¡¿`© 588 nm H$m EH$dUu àH$me AmnVZ H$aVm
h¡ & And{V©V àH$me H$s Va§JX¡¿`© Am¡a Mmb kmV H$s{OE & Ob H$m AndV©Zm§H$
4
h¡ & 5
3
.55/3/1 18

36. (a) Derive the expression for the force acting per unit length between
two long straight parallel current carrying conductors. Hence
define one ampere.
(b) Two long parallel straight conductors are placed 12 cm apart in
air. They carry equal currents of 3 A each. Find the magnitude and
direction of the magnetic field at a point midway between them
(drawing a figure) when the currents in them flow in opposite
directions. 5
OR
(a) Draw the schematic sketch of a cyclotron. Explain the shape of the
path on which charged particle moves when the particle is
accelerated by it.
(b) To convert a given galvanometer into a voltmeter of ranges 2 V, V
V
and volt, resistances R1, R2 and R3 ohm respectively, are
2
required to be connected in series with the galvanometer. Obtain
the relationship between R1, R2 and R3. 5

37. (a) What is meant by plane polarised light ? An unpolarised light is
incident at an angle  on the surface of glass of refractive index .
If the reflected and refracted rays are perpendicular to each other,
then obtain the relationship between  and .
(b) Two polaroids P1 and P2 are placed in a crossed position.
Unpolarised light of intensity I0 is incident on P1. If P2 is rotated
through an angle  about the direction of propagation of
light, keeping P1 fixed, plot the graph of intensity of light for
0 <  < 360 which is (i) transmitted by P1, and (ii) transmitted
by P2. 5
OR
(a) Briefly describe the Young’s double slit experiment of interference
of light. Drive the expression for fringe width in the pattern.
(b) Monochromatic light of wavelength 588 nm is incident from air to
water interface. Find the wavelength and speed of the refracted
4
light. The refractive index of water is . 5
3

.55/3/1 19 P.T.O.