Class XII Physics 2012 Question Paper (Set 1) by gyanguru

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This is the Set 1 of the Physics question paper of Class XII CBSE (Central Board of Secondary Education) examinations.

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									    I Series      : SMAIl           I                                                                                                 .~.
                                                                                                                                      Code No.             55/1/1
    -m.r~.                                                                                                       ~                ~   cpf ~-~                  ~ 1f9-1f!B'

    Roll No.                                                                                                     'R~ml
                                                                                                                 Candidates must write the Code on



-
                                                                                                                 the title page of the answer-book.



        •    ~~CR'Bfcp~~-LBT~~1f!B'l1                                                             t   I
        •    ~-LBT~~m'4ctr31k~~~~cpfwr~-~~1f9-1f!B''Rm                                                                                                     I

        •    ~~CR'Bfcp~~-LBT~30~t                                                             I

        •    ~~Cf;l'3T\"frM&""IW~-«~,~Cf;l~~~                                                                                         I
    -   •    ~    ~-LBT cpf ~                 ~ ~                    15 fl:r;rGCf)f~             WIT Tf<iT ~ I ~-LBT Cf)ffqmur ~                       ~ 10.15 ~
             mr~             110.15             ~~                   10.30 ~(lcpwr~~-LBT~~~~~~~~-
             ~'RCl#~~~1
        •    Please check that this question paper contains 11 printed pages.
        •     Code number given on the right hand side of the question paper should be written on the
             title page of the answer-book by the candidate.
        •    Please check that this question paper contains 30 questions.
        •    Please write down the Serial Number of the question before attempting                                                                   it.
        •    15 minutes time has been allotted to read this question paper. The question paper will be
             distributed at 10.15 a.m. From 10.15 a.m. to 10.30 e.m., the students will read the
             question paper only and will not write any answer on the answer script during this period.


                                                                    ~fCl~IW=t                             (~)
                                                                            PHYSICS (Theory)

    f.relfftrr   WP! " 3   crutJ                                                                                                                [~3fcn,'   70
    Time allowed " 3 hours                J                                                                                               [Maximum marks,' 70




                  (i)      ~rrR'~t                                     I
                  (ii)     s« rrR'-W                'R'     ~        30 rrR't I rrR' 1 '# 8 ncncf;' rrR' 31frr-HY,3f1«74 rrR' t                            3#r ~       f!C1i
                           3fcnCfiT     tI
                  (iii)    rrR' 9       '# 18             'R'   ~          rrR' qj-3fcn           t;
                                                                                              CfiT rrR' 19      '# 27   'R'   ~       rrR'   rfFr 3fcn         t
                                                                                                                                                           CfiT 'ff'2lT rrR'
                           28   '# 30     'R'   ~                    rrR'   rikr 3fcn     CfiTtI
    55/1/1                                                                                1                                                                        [P.T.O ..
                (iv)      ~-q;r # "flrm W cnTt~              ::rif t I ~        qt 3fq;J ~                                   ~~                 #, rfFr 3fq;J ~            ~
                          ~ # 3#r rifq 3fq;J ~ M JTRT # 3iIPflRCf) qq;:r                                                 ~              fcFi<:rr rp:ff   t I # JTRT #
                          3fTTTc1iT m TJ<l qq;:r # -# cficrM ~~        it Cfif.:rr t I                                              .

                (v)       c$H¥H2<           cf;- ~           qff 3F]11frr   o:rtt. t I ~              ~       3i16f:(2/Cf) 6T       nT 3TJq HEjJIOICf)74           ?JR71lT CfiT
                          w:WrCR"~t                      I
                (vi)      ~        3i16f~4Cf)    6T 3TJq HAfMf@H             ~             H4HiCf)r       cf;-1fFif CfiT ~                 CR" ~             t:
                                        c    =   3 x 108 m1s
                                        h = 6.63 x 10-34 Js
                                        e = 1.6 x 10-19 C
                                                                                                                    \/       t:          ~71             R ~
                                         !-!o = 41t       x 10-7 T mA-I                                                                   ~

                                        --
                                             1
                                                     =   9 x 109 Nm2C-2                                                       t;:        ~?l         (       t'<oA III.)   )
                                        41tEo                                      .                                    /  1a                                 1
                                        me       =   9.1 x 10-31 kg
                                                                                                                     1// ~ ~ t                  r        to       A-

General Instructions :                                                                       ,                    }:                                ~J
     (i)   All questions are' compulsory.                                         ,I {e.)                                                         JJ               ¥
     (ii) There are 30 questions in total. Question Nos. 1 to 8 are very short answer type
           questions and carry one mark each.
     (iii) Question Nos. 9 to 18 carry two marks each, Question Nos. 19 to 27 carry three
           marks each and Question Nos. 28 to 30 carry five marks each.
     (iv) There is no overall choice. However, an internal choice has been provided in one
           question of two marks, one question of three marks and all three questions of five
           marks each. You have to attempt only one of the choices in such questions.
     (v)   Use of calculators is not permitted. However, you may use log tables ifnecessary.
         (vi)         You may use the following values of physical constants wherever necessary :
                   c = 3 x 108 m1s
                  h = 6.63 x 10-34 Js
                   e = 1.6 x 10-19 C
                   !-!o = 41t       x 10-7 T mA-I

                  _1_          =   9 x 109 Nm2C-2
                   41tEo

                   me     =    9.1 x 10-31 kg



1.       M ~ ~$JlCf?;I•.;'j cnr f.:p:;, fcrqq ~ ~                                fcrqq Cfft -31R          ~        mm t cp;rr~                           ~        ~ ~
         fen ~         c);-~       $JlCf?;I'i ~          m ~ ~ TIfu CR" w t ?                                                                                                  1
         When electrons drift in a metal from lower to' higher potential, does i't mean that all
         the free electrons of the metal are moving in the same direction?

55/1/1                                                                                 2
2.       M      ~        1K ~           ~ iJ)kI<il4 ~       Cf)f~                     B
                                                                                 CR:Cf)     t 31tt ~             1K ~               60°
                                                                                                                               CfiTur      t    I~       1K
         ~     ~ iJ)klCh14 ~             ~~                       l1H
                                                          CR:Cf)Cf)f ~                     ~          ?                                                            1
         The horizontal component of the earth's magnetic field at a place is B and angle of
         dip is 60°. What is the value of vertical component of earth's magnetic field at
         equator?

3.       MM~cit~cit('lN-~Cfl1~lJ1111(~"#'~                                                                                                  I                      1
       Show on a graph, the variation                                    of resistivity                   with. temperature              for a typical
     . semiconductor.

4.       M~~~~~~Cf)fl1H~Cf4T~~?                                                                                                                                    1
         Why should electrostatic field be zero inside a conductor?

5.       '3'ff ~'Dfu              Cf)f;w:r~             ~            f.:1cffi:r"#1H, 1
                                                                                l               mm otrr ~                cit   ~"Otrif      (Mf 1600        A
                             ~m~~t
         cit q{I~II41 fqfCfl{On                                              I                                                                                     1
         Name the physical quantity which remains same for microwaves                                                                    of wavelength
                         ~   I                ~                      o
         1 mm and UV radiations of 1600 A in vacuum.

6.       fcRr ~         "# ~       ~                    Gfjf~
                                              3iqCjdOiiCfi                             'ffir,   M          ~     "# ¢          1K Cfitq cit ~           ~
         ~cit~~~?                                                                                                                                                  1
         Under what condition does a biconvex lens of glass having a certain refractive index
         act as a plane glass sheet when immersed in a liquid?

7.       m"#~~~~'I'                               31tt'2'    ~m~1K~t                                           1~(ffi""#~~'tlffiICf)f
         l1H   ~~~~wm,                                ~      '1' 31tt '2' "#mt;~'tlfficit~CFlTmrrr?                                                                1
                                                                         0
                                                                         1
                                                                                                 ••
                                                                                            I
                                                                         20
         Predict the directions of induced currents in metal rings 1 andZ lying in the same
         plane where current I in the wire is increasing steadily. oJ
                                                  .                      10
                                                                                    >       I ••
                                                                         2   O~
8.       it-~                           Cfl1
                        cit qRCfi(>'qOiI3lT ~                    I                                                                                                 1
         State de-Broglie hypothesis.


9.       Cfitq ~ M               W1 ~     ~       ~    m Cf)f~qCjdOiiCfi(I-l                    g)    =~        t   I~     1K ~            ~         cit ~
         ~,         ~        ~~,          ~           3ITtlK ~           ~ ~41'"f1{T[1f1              Wt            m, ~ ~               Cf)f~         CfiTur
         ~~?                                                                                                                                                       2
                   l
         A raY_?-fighh incident on an eiluilat~J~~s§-Prism-4tg       =~)     moves' parallel to the
         base-line of the prism inside it. Find the angle of incidence for this ray.

55/1/1                                                                             3                                                                         [P:T:O.
10.      fsM2M (~~                             Q'"lIMlll (~~#                      -3RK(~              fufur<t     I                                        2
                                                        ~.




      ~          ~               #, Rkif<:1f@(1 # ~               GT ct-~        Cf?T
                                                                                    ~              ~           I

         (i)     s:1':R~,1m
         (ii)    ~               (9)'"l{lq~Cf)

         (iii)   s:1~412{~
         (iv)    ~'lffiCf)~

         Distinguish between 'Analog and Digital signals'.
                                                                           OR
         Mention the function of any two of the following used in communication system:
         (i)  Transducer              ..--<

         (ii)    Repeater
         (iii)   Transmitter
         (iv)    Bandpass Fitter
                                  1        /




11.      "Q"Cf)"~ Cf?T~                   ~~             ct.~.~.)          E ~      3iH1f{Cf) ~                    'r' ~   I ~    ~           cnT ~ ~
         ~R1                ~R2                ~"Q"Cf)"~~~~lFIT~                                   1~#~Cf?TllRf-ikiifChC1

         ~~~#lWlTlFIT~:                                                                                                                                     2
         (i)     ~~#cAt~~~~                                                 I

         (ii)    ~~#~R1~~                                             I

         (iii)   ~      ~             #   R1 ~         R2 ~       ~       # ~41f"1C1' t       I·

         (iv)    ~      ~             #   R1 ~         R2    m (*14iC1{)~           # ~41f\J1C1        t   I

         dq{1Cffi~          ~                    # ~         mu31T ct-llR,        0.42 A, 1.05 A, 1.4 A ?MT 4.2 A                         t   I~,       ~
         3ilq~4Cf) ~              ~ fcfl ~          mu31T ct- ~           llR    dq{1Cffi ~                    ct- ~       #   m m I m, dq{1Cffi
         ~~ct-m~#~muct-llRCfJ1~~                                                                                   I

         A cell of emf E and internal resistance r is connected to two external resistances R1
         and R2 and a perfect ammeter. The current in the circuit is measured in four different
         situations:
         (i)     without any external resistance in the circuit
         (ii)        with resistance R1 only
         (iii)       with R1 and R2 in series combination
         (iv)        with R1 and R2 in parallel combination                               ,
                                                              •                           l\~\         ., <,           it "\          ,.J )
                                                                                                                                      1




                                                                               4:2 A,
         The currents measured in the four cases are dA2 A, t.05. A, 1.4 A and ••...~~~P'- but not
                                                                  ('    ~    ,
         necessarily in that order. Identify the currents corresponding to the four cases
         mentioned above.


55/1/1
                            (\    I
 12.    00           iJ)klChlll ~         "Ch1
                                             iJ)klChlll ~       -       2.6 x 10-5 ~ I ~                    ~            fcn ~       fcRl ~       cpr
           iJ)klcNlI ~             ~? ~~          lJuIT cpr~            ~             I                                                                    2
                                                                                                                5
        The susceptibility of a magnetic material is - 2.6 x 10- . Identify the type of
        magnetic material and state its two properties.

 ~.     ~ ~               cF"1ICflI{    om P ~        Q .q.~"Ch1            &arr R ~~              ~4HIl1~(1 ~             'I' ~             m-   w~
            I ~fq;r.q.             ~~             ~~~WTTflfT~fcn~~~¢~                                                                ~klqttt      ~
        ~ ~ ~ it ~                          1f{   t   I~    ~       ~           1f{   -;)c: iJ)klChlll ~    cpr l1H      ~       ~           fWT ~
        ~I                                                                                                                                                 2
                                                                        Q
                                                                        I

                                                           p                •
                                                                I



           Two identical circular wires P and Q each of radius E. and carrying current 'T are
           kept in perpendicular planes such that tney have a common centre as shown in the
           figure. Find the magnitude and direction of the net magnetic field at the common
           centre of the two coils.
                                                Q
                                                                        I

                                                           p                •




  14.      \iftif   00     ~         ~          coT00       m.m. ~               ~ ~ ~~                             M     \j'ffiIT ~   ill   Cf# ~
           ~             ~ mm, ~, ~.m. (~flOjlqffi) ~ -mo cpr ~                                      ~      1f{ ~11I(11<
                                                                                                                       ~               ~          mm
           ~~            I ~-~"Ch1                :8Cfl0F"I ~~1f{~01IT&IT~"Ch1\jff~~?
                                                          I                                                                                                2
           When an ideal capacitor is charged by a de battery, no current flows. However, when
           an ac source is used, the current flows continuously. How does one explain this,
           based on the concept of displacement current?


t15.       00        ~
           coTOO~fWt~~(~~
                           3Wffi        'Q' ~ ~ 'r' ~"&4, (i) ~~
                                                                        I
                                                                                            (E) ~        (ii) ~          fcrqq   (V) ~ qRq~"i
                                                                                                                                                            2
           Draw a plot showing the variation of (i) electric field (E) and (ii) electric potential         d-- '
           (V) with distance r due to a point charge Q.                                            \/;:):;

  ~00~~~-~"Ch1~~                                                             1~~fcn'L'                     ~-~"Ch1oo~.q.I

           ~ ~                 ~        ~ fWt   ¢:tlq~lICfliJ)klcNlI ~           cpr l1H 2 u2 mrr~                  I.                                      2
           Define self-inductance of a coil. Show that magnetic energy required to build up the
           current I in a coil of self inductance L is given by ~ U2.


  55/1/1                                                                         5                                                                    [P.T.O.
  17.   .am ~~                       -It~          'tffiT CfiTl1R (~mA),     ql?ilf~f~ICfi~        -It~         'tffiT ~l1R     (~ JlA) ~
        ~~                     t   11ft m::nm ~CfiT            ~           ql?ilf~~ICfi ~       -It~ ~           ~       t?                    2
        The current in the forward bias is known to be more (-mA) than the current in the
        reverse bias (-JlA). What is the reason, then, to operate the photodiode in reverse
        bias?


y.      fmT
           'L'     ~
                   'L'     ~
                               CI?T~        'tWl CI?T~~,
                                    ~ 'tWl ~ ~
                                                              '0)'   cnlufr:r ~         ~ ~     WiiIT ~
                                                        cwr:r (WT) ~ ~ 1R ~ ~ t ~ cpm fmT cwr:r CI?T~
                                                                                                                ~        t fen, ~      ~

        1R~t                   I ~CI?T~~,                cwr:r (WT) ~~~~~t        ~cwr:r~~~<1klq~
        t I~ ~                     ~ ~          W1R    iJ)klCf?l~ B, ~ fq~4H t I cwr:r (WT) ~ ~ ~ cwr:r ~
                                                                ~
        ~t~.~.                     (fcIwr~GWl)              ~m~~~~                                   I                                         2
         A metallic rod of 'L' length is rotated with angular frequency of '0)' with one end
         hinged at the centre and the other end at the circumference of a circular metallic 'ring
         of radius L, about an axis passing through the centre and perpendicular to the plane
         of the ring. A constant and uniform magnetic field B parallel to the axis is present
         everywhere. Deduce the expression for the emf between the centre and the metallic
        .nng.


   19. ~-It~LCR         ~~~l"p:ITt~,                                              L = 5.0 H, C = 80 JlF ~                     R = 40   nt
----------/~ ~ 240 V ~ ~ '1ftqffi ~                           ~~ ~          fi41f~C'I   t   I qRCfiW1 ~             :                          3
                                                                      R


                                                                                               C


                                                                      L
           (i)         ~       CI?Tcnlufr:r    ~       ~~          1R ~         CfiT qRilif(>lC'lCRffi    t
           (ii)        ~~1R~CfiTl1R,

           (iii)       ~1R~~fuff~~crt~lFf(3W.~.~.)                                                       fcrqq-1:ffi1I

           The figure shows a series LCR circuit with L = 5.0 H, C = 80 JlF, R = 40                                                        n
           connected to a variable frequency 240 V source. Calculate
                                          .     R



                                                                                               C


                                                      L
           (i)         The angular frequency of the source which drives the circuit at resonance.
           (ii)        The current at the resonating frequency.
           (iii)       The rms potential drop across the capacitor at resonance.

  55/111                                                                    6
20.      00 4 em        x   10 em ~               (3WfTll) ~~'3i14f11Cf)1{                  ~ ('lm) ~ 2 A CfI1~~~
         m -m ~ I fq;f (~                -q: ~            11<l3fF1K,          ~~            ~"ill{  f;rml 5 A ~                       ~        ~          m
         -m t ~-qm ~             ~ 1ffiI' ~Pl<rr ~ I ~                        ~"ill{ ~          -qm ~          tr 'Wl(ffi -q: m 'ill ~             ~            3

                                                           I=5A
                                                                             4 ern

                                                          2A                                 2A
                                                                         10 ern




                                                          1 ern
         (i)    -qm~lf{~qwrr(~~-~~~
         (ii)   ~    ~"ill{          ~ CfiRUT, -qm If{ ~                      cnB ~        CfiTllftmuT (l1R) ~            ~        fWl I
         A rectangular loop of wire of size 4 ern x 10 em carries a steady current of 2 A. A
         straight long wire carrying 5 A current is kept near the loop as shown. If the l~and
         the wire are coplanar, find

                                                           I=5A
                                                                             4 ern

                                                           2A                                2A
                                                                         10 ern




                                                          1 ern
         (i)    the torque acting on the loop and -                        /
         (ii)   the magnitude and direction of the force on the loop due to the current carrying
                  .                         ~
                WIfe.        r?---       -:If ~

21.      (31)   ~    ~ ~             ~            ~         ~      Cfqh~.')Cf){OI ~            ~          ~              ~ ~              ~ ~            fcp
 '"             t51~~l\l'H CfI1ncff'      ~           ~           -q:,   ~JlCf?;I'i CfI1~              CfiT l1R" ~       (~JlCf?;I'i ~         ~        m-
                w-ffi   fI<II~t4 ~l1R" CfiT n 1fIT                 men- ~       I                                                                                3
         0f)    00 t51~~hH           ~            -q: ~         ~JlCf?;I'i    mtq -q: ~            ~            ~        -q: ~   I~        ~       ~~Cf?;I'i
                3llRT f'"lk\fllOi ~                (-3lID ~                  -q: ~       \i'frl 'ill dfflMfI        m~        qrffi ~Cf?;lOj') ~31T
                CfI1~            ~            fcmRt mm ?
         (a)    Using Bohr's second postulate of quantization of orbital angular momentum
                show that the circumference of the electron in the nIl!orbital state in hydrogen
                atom is n times the de Broglie wavelength associated with it.
         (b)    The electron in hydrogen atom is .initially in the third excited ~tate. What is the
                maximum number of spectral lines which can be emitted when it finally moves
                to the ground state ?

55/1/1                                                                               7                                                                     [P.T.O.
                                                                                                                                                                           \

                                                                                                                                                                     ~.
                                                                                                                                                                      ,(       "0
22.      ;mW"#~CfiT~~(ffi"                           AB ~11<IT~,                       Fm#~~~~~R<m
         (3iqfhhil) fcrqq >fCJUTill rmD     ~    I~ ~                   ~        ~
                                                                             CfiT,           ~    ~   q(Yf   ct.~.~.)    81 ('MT
         82     t,   ;mW"# ~       TT<l ~           B<ilF~d fcn<:rr ~ I ~
                                                                  11<IT                          m~   fcr~ ~            (~
      ~              A fut-B 120 ern ('MT 300 em         ¢'R'~m-illt                   I illmd"~
         (i)         8/82
         (ii)        ~E1~m~~~(~~cR¢                                                          I                                     3'
         ~                              ~
                       cRB~~'i!?nMdl CfiT ~                    \1fRfT ~ ?

                                     .----~          I 11----'\I\.KI\;f\,----.



                                     IE----        300 em --~)
                                                120cm~
                                  A\--------..,.-~------'B


                                                              t2
                                                                   ~
         fCflNICfl ~        mm CfiTMrr ~            ~~                 "# :m=m=r   ~         RCfiT md"~,
                                                                                                 11R               .4        Q
         ~-BCfiTt~~~m                                    IA3i1rD~~~CfiT11Rmmd"~                                          I
                                                    1n         E
                                            F                                            D

                                        In                         4n                        R




                                            A
                                                I    Lt----'
                                                    9V         B            3V           C

         In the figure a long uniform potentiometer wire AB is having a constant potential
         gradient along its length. The null points for the two primary cells of ernfs 81 and 82
                                                         (~                                                    \

         connected in the mariner shown are obtained at a. distance of 120 em and 300 em
         from the end A. Find (i) 8/82 and (ii) position of null 'point for {he cell 81,
         How is the sensitivity of a potentiometer increased?
                                     .-----i I It-----J\/V'(/\I\,.----,


                                     IE----        300 em --~)
                                                120cm~
                                  A~------..,.,.--~------'B




55/1/1
             Using Kirchoff's rules determine the value of unknown resistance R in the circuit so
             that 'no current flows through 4 Q resistance. Also find the potential difference
             between A and D.




                                            A
                                                I    Lt--~-J
                                                    9V    B            3V        C

23. . (i)           CWfTUl ~      (A) ct 30 Cf 170 ct~    llRl, ctm,   ~ ~-3lR"$:R         ~ (BElA) ct
                    lWf ct~      ~ ctr ~        ~cwil4 ~ ct~       ~lJUT      ctrnr ctr ~ ~       t?
             (ii)   ~       fcf>~      ct~~"!lftw#             ~CfiT     ~   ~     (f.:rm) Will t ~~
                    ~0lI4H ~       (A) w ~      (-311f~ ~ ~      I                                                       3
             (i)    What characteristic property of nuclear force explains the constancy of binding
                    energy per nucleon (BEl A) in the range                 of
                                                                      mass number' A' lying 30 < A <
                     170 ?
             (ii)   Show that the density of nucleus over a wide range of nuclei is constant-
                    independent of mass number A.
24.          00 fur.wr cnT41'§f<?1n fi8 ctr 3iIct~lICflnl t ~
                                  C                     c     ct ~                   #   cJ "Cfllt WCf)~
                                                                                                 C            I          3
                 00 \iiqlct¢f>lll dirT w,OO 41'§(1Cflfur.wr ct
                                ~                                   ~                         ~ ID1{f, 3W1Tl141'§f<?1n
             dirTCfiT~ctm,        ~~~             I
             Write any two factors which justify the need for modulating a signal.
             Draw a diagram showing an amplitude modulated wave by superposing a modulating
             signal over a sinusoidal carrier wave.
25.                      CfiT
             3i1~"1f2I~"1 ~-~               '84ICfl{OI
                                                     ~     I~   ~                      c
                                                                        ctr ~ '84ICfl{OI nT~-1k1CfJlll
                      cttnTiR-m
             fClfCfl{On               ct~       rm ~ ID1{f ~   ~"'8"Cflmt?                                               3
                    WPM ~       >I'llIcf ct &r ~         oourr
                                                         CfiT~      ~      ~                 c
                                                                                ~ '84ICfl{OI t ~       ~
             ~ctr~~tl
             Write Einstein's photoelectric equation. State clearly how this equation is obtained
             using the photon picture of electromagnetic radiation.
             Write the three salient features observed in photoelectric effect which can be
             explained using this equation.
 26.         (31)   ~                 ~
                            OlIf('1Cfl{OI >W{f Cfi8 ctm          qi~fn:j~,~-mffi ~
                                                                             CfiT         ~3ilct~4Cflt?                  3
 '01)               <:frr ct~~          w:ITrr #, A dirT ~       ct ~CflctOn PM CfiT
                                                                           W       ~      ~     lFIT t I ~       ~
/                   ct ~ ~         w, ~ 1f4RK A          t~         ctr mwrr K ~     «(Rc:) t I 01, ~ ~          w

                    WPMctrmwrr~~~w~~t                                       I
             (a)    Why are coherent sources necessary to produce a sustained interference
                    pattern ?
             (b)    In Young's double slit experiment using monochromatic light of wavelength A,
                    the intensity of light at a point on the screen where path difference is A, is K
                    units. Find out the intensity of light at a point where path difference is A/3.

    55/1/1                                                         9                                               [P.T.O.
27.      ~           c)? ~        c)? ~             ~ 00           ~           fuRt   00 fq-qcf.:r ~               ~            cn1 cxn&rr~,                    ~ fuRt
         QCf)qOn~             ~       00 ~            ~ I                                                                                                                      3
                 ~ fuRl cn1 ~                     CfiT~        mtm ~                          ~~ 1fIT ~            ~            ~"ill,     ~           ~         fq-qcf.:r
         ~c)?~~~1:R"CFn~~                                                      ?
         Use Huygens's principle to explain the formation of diffraction pattern due to a
         single slit illuminated by a monochromatic source of light.
         When the width of the slit is made double the original width, how would this affect
         the size and intensity of the central diffraction band?

28.      "QCfl
             ~        ~       c)? ~               CfiT~        ~           ~              ~         fyf"FH     ~        CfiTR:cn1 ~                ~             mco      m
         ~~I                                                                                                                                                                   5
         W~CfiT"QCfl41'l'1'"1Iqct      ~~             a&~                                         Cf)1~fC!R:lCfiT~~                        I CFnW~oo
         ~~~cn1                   d-c'Clct4 WllT1:R"CfiTt~m~?                                              ~~                          I
                                                                           are:rcrr
         (.:31) ~1R1CRlcn1~~                                            I WCfiT~.~.                   (S.I.) ~CFn~?
         01)     TTm1 c)? ~               c)? ~           00   ftr.& ~                fcn,        00"QCfl"W1R               ~      ~ ~                 -3FRf W«Wf
                 WR:~             c)? Cffi1JT00            ~           1:R"
                                                                          ~           ~           CfiTliR, ~           ~ ~         ~       cn1 ~              f.:M\
                                                                                                                                                           1:R"       ~
                 ml
         0)      w~           cn1 mrr CFn          mm, ~WR:                ~              (i) ~HI~~lct        m (ii) 5fi01I~~lct m ?
         Explain the principle of a device that can build up high voltages of the order of a few
         million volts.
         Draw a schematic diagram and explain the working of this device.
         Is there any restriction on the upper limit of the high voltages set up in this machine?
         Explain.
                                                  OR
         (a) Define electric flux. Write its S.1. units.
       , (b) Using Gauss's law, prove that the electric field at a point due to a uniformly
                charged infinite plane sheet is independent of the distance from it.
      I, (c) How is the field directed if (i) the sheet is positively charged, (ii) negatively
                charged?
29.      'i<i!O!(\Cf)cn1~@ffiTcn1~C'MT~m~~                                                                              I                                                      5

         00      ~        'i<i!O!(\Cf) ~
                                    c)?                     a& ~                   cn1 ~              ~~:                       150 em·~               5 em     t     IW
                   ~
         'i<i!O!(\Cf) 3 km        ¥~,              100 m ~             ~              w \l'fTCt "ill~
                                                                                   CfiT                                 ~fctf~kI cn1 ~                      ~         mm
         ~     ~fctfiiikl ~           ~ 25 em ~                ~
                                                            1:R"           I

                                                                           .are:rcn
         ~~m CfiT~                              c)?
                                      'i<i!O!(\Cf) ~               ~ fcRr ~                   ~       m      ~ ?

                  00~~c)?~~~cn1~~~:                                                                                                1,25 em ~                 5 em     t    I
         ~       30 CfiTufr:r~                mco ~ c)? fWt, ~ CfiT~      c)? ~&:r                                                ~        mTfur~,                     ~
         ~~           CfiT~           ~      it M~ ~ ~14Io:ljct: M\ifffiT ~ ?

55/1/1                                                                                10
         Define magnifying power of a telescope. Write its expression.
         A small telescope has an objective lens of focal length 150 em and an eye piece of
         focal length 5 em. If this telescope is used to view a 100 m high tower 3 km away,
         find the height of the final image when it is formed 25 em away from the eye piece.
                                                OR
         How is the working of a telescope different from that of a microscope?
         The focal lengths of the objective and eyepiece of a microscope are 1.25 em and
         5 em respectively. Find the position of the object relative to the objective in order to
         obtain an angular magnification of 30 in normal adjustment.
30.      CE fcR"m ~ 00              S;if"1«O{ ~         ~   m~ ~ ~ ~ ~                                       I~       cnr<:T~      CfiT

         ~~             I ~~fcnw~CflT~~                                              Av = - PacRL, ~              Pac - '1:lRT~,
                                                                                              rj
         RL -~~~rj-f.:r<ffi~t                                  I                                                                          5
                ~~~m~~5fiOII\4CflmCfiTcp:rr~t?
                                                               ~
         (31)   ~     ~ ~       ~       <itlCflI<l m
                                                 ~             ~        ant@ ~           ~    p-n ~               ~         ~
                                                                                                                         CfiT
                M      ll<IT  m I~         ~   ~ CfiT ~~                        ~     Hcrm ~ f.:rrRf ~            ~   CfiT ~         I
         (Gf)   f'"l8ifCfl('1 mm A       ~ B ~     m f.:rrRf       ~        ~       (Y) CfiT ~           :
                (i)     OR ltc ~          (ii) NAND ltc
                                           t1      t2 t,       t4 ts t6                      t8
                                                   I           I        I                    I
                                                   I           I        I                    I
                                                                                             I
                                                                                             I
                                                                                             I
                                                                                             I
                                         Ai----f


                                         BI-: --   •••••...•
                                            I
                                            I
                                            I


         Draw a simple circuit of a CE transistor amplifier. Explain its working. Show that the
                                    - - ------------            P R                                           I




         voltage gain, A~, ofthe amplifier is given by Av = -                               a;, L, where Pac is the current
                                                                                                     1

         gain, RL is the load resistance and rj is the input resistance of the transistor. What is
  __ the significance of the negative sign in the expression for the voltage gain?
                                             OR
      (a) Draw the circuit diagram of a full wave rectifier using p-n junction diode.
            Explain its working and show the output, input waveforms.
      (b) Show the output waveforms (Y) for the following inputs A and B of
            (i)   OR gate     (ii) NAND gate
                                           t1      t2 t3       t4 ts t,                      t8
                                                    I          I        I                        I
                                                    I          I        I                        I
                                                                                                 I
                                                                                                 I
                                                                                                 I
                                                                                                 I
                                         Ai----4




55/1/1                                                                 11

								
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