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Class 10 CBSE Pre Board 2017 : Physics

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Rupesh Kumar
Smt. Lilavatibai Podar High School (LPHS), Mumbai

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stsi. Series : OSR/I Code No. sslll2 3f,{-5rwfir s.{q-YB dni.. q{ qqrq Roll No. Candidates must write the Code on the title page of the answer-book. fut} r o !ffirqiqo,-{i} toqs vrt-rl,t { Eidf, gs 15 t o HFr-rr fr qriEi 6rE ftt ertriqq rrq Ets'rqr *i 6H cr{-5fitrs, *.{e-Y*qrled o gtl-{ drq qr .i fl*.gs qFt-rt it so qF t o StrrlTtrFtq.T 3-f,{frq.{rEsur*rt q6d, qrt ot xqiq' wqfqfntl . EqqFT-Er dr r6i +fuq ts fu+aifl {rqzr fqqT rrqr t r qn-.rd or fuawrWRq i[ to.ts qi flsqr qr+qT I 10.15 qq t 10.30 qi ro or* *-q-e qFt-wt fti qi,t efu qs erqtl + ftH A r r r t e+r-gfir*r qr *t$ o o o o o wt reT fui) t Please check that this question paper contains 15 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 a.m., the students will read the question paper only and will not write any answer on the answer-book during this period. $)ftro,flildm C*' TFffi) fuiffudtr Time : 3 PHYSICS (TheorY) Eitl (i) (ii) wrlmwetW* (iii) (iv) (v) r+- ivw qfd-dyt\q ff?d'*pqd6-fr r yntg dra # slqsfl Et ai w*, sw tg d zr if vdqwq aTqiiqw*aqrvw 2s I so i s46v?q frq eiqw * t dhffiqtde{iff d<'ofs eiltttftaswt r w7w if aqrt rr *H fu +d * I dqtfu, d ffi arLd Wwt il, dh tiqit ad V6 yw t ofu {tq oi6f qld dH ywf t'J s17afuaqq yqrq fuqr TqT t / dC aw} it zltwl I?d q+ 55nt2 70 r Wsq7wif yaSO rffif tynr l da aiqwt :70 I Maximum Marlcs : allowed: 3 hours I wqrqfr*vr: t srfqadq eiq qrif it d #ftr wwr a7 I 51q { 1 IP'T'O' (vl *a-fdzr- * dqqhT *7 eAqA sqhrwrrqrdd- r (vii) qrt oilqyqtdl wq ?E? * r aqrfr qfr emtqq al al enq dgqaffi?q wrwft w ffifud q)futfrqdiqif nqni w aqqlr qE nm-d f,, c:3x108m/s h:6.63 x 10Ja Js e: 1.6 x 10-19 C Fo:4xx l0-7TmA-l 1 x loe Nm2 c-2 G:9 m.:9'1 x 10-31 kg Generul Instructions : (i) (ii) (iiil All questions are compulsory. There are 30 questions in total. Question Nos. questions and caruy one mark each. I to I are very short answer type Question Nos. 9 to 18 carry two marks each. Question Nos. 19 to 27 carry three carryJive marl<s each. marl<s each and question nos. 28 to 30 (iv) (v) (vil (viil One of the questions carrying three marks weightage is value based question. There is no overall choice. However, an internal choice has been provided in one question of nuo morlcs, one question of three marlrs and all three questions oflive marks each weightage. You have to attempt only one of the choices in such questions. Use of calculators is not permitted. However, you may use log tables You may use the following yalues of plrysical constants wherever necessory : c:3x108m/s h:6.63 x 10-34 Js e: 1.6 x 10-19 C Vr:4xx 10-7TmA-l I -;-:9 +fieo x 109 Nm2 C-2 m":9'1 x 10-31 kg 55nt2 if necessary. 2 t. ffi qeo+i t{d qk'rs-dr s1qfrqm *rsr*.r s.r. qrr*.frfug r Define the term 'electrical conductivity' of a metallic wire. Write its S.L unit. 2. ffi qrdril{q 6ffiO *t gq u-+nftrsfqd flq.qr ,rqr t C(t): 5 sin(lOzrt) : volt st$ qr$ffi forqi{ qvriq q-{qr q,t ili.r t r qrge=T qErsis.rlf, +iflqq r 2 m(t) Etris{ tt-+-sif The carrier wave is represented by C(t): 5 sin(l0nt) volt A modulating signal is a square wave as shown. Determine modulation index. 2 m(t) in volt t in second a J. qrs if nrq * qrpT si *1qftrtr{silr *r kqtur qflf{q r Show variation of resistivity of Si with temperature in a graph. 4. ffi urrt Ftq *i ffi wrae qqrr + {FrrS ii ror rrqr t r gq {*sH * e+q q{ {qlq{ t 20 cm$ w fiprd ffi ffisn kq *l yfrkq {S fqq +{qrfi t r iis +i sls'q $ wt tz A convex lens is placed in contact with a plane mirror. A point object at a distance of 20 cm on the axis of this combination has its image coinciding with itself. What is the focal length of the lens 5. "flm-s Etdr t $ eTr+{r r" w ? ffi k{t.Jq{i fuqrs +fdq, ser{ *1gfudfqq q-6, qqfrr1q ggfu{d q+d + qFrf,Es{d r "For any charge configuration, equipotential surface through a point is normal to the electric field." Justifu. 55ll12 lP.T.O. 6. ge-drq eir B t +'r V t ffi * +nur Filt{-q gqslq qe F *- fleq Hiqvr Fq r vq gls+iq qld dr krn wr t z { t*qofmfuq rrioqn sil-n{r Write the expression, in a vector form, for the Lorentz magnetic force charge moving with velocity magnetic force ? 7. +n ffi sd frfuq t- rl due to a ? in a magnetic field B. Wfrut is the direction of the qrq+. {iqrc qc[ rT sr Ri-s 3iliq frqr rrqr eftrg*r*r F --- t | 'x' ERI rrqikd orcrftt 6t .rnqrfrq - - - - - -l I !l-JI r1fir qln frf'* frn*o" The figure given below shows the block diagram of a generalized communication system. Identi$ the element labelled'X' and write its function. - - - -l t- - - 1l stTFT Tr{q + q{ fl,rnq q-i t d r rilirqr, q+i t Message Message Signal Signal ffit q*. qrq 6T ?rn Es{r oiq or t, Em Fq qt-{ Hr rtr rs qrfr qr.rcd qg+n ek Bit r t sqsa ffit E-rtr Two spherical bobs, one metallic and the other of glass, of the same size are allowed to fall freely from the same height above thr ground. Which of the two would reach earlier and why ? 9. 55fit2 ffi if ac tq * qr*l d"hfiq it 1furirr 'C', sfiffi qftRltr* 'R' defl 6t$ GrGr 'B' {qikd t r qw EE qrs'*'qrrr qf,dr t r qk (i) qftR}r-+. B 6} qqsq w6T, {qriu ft1 qifsrcit + +q st* qtr+qil qfr*r rq fi qK, (ii) qrRdT *t vqrq rcrrr qftrdtrs'n tl qf;r w qt qrq, d *q +t qq-oil q1 qfiffi tt'n z qfltq q-{sr qfrw{ oR' and a bulb oB' are connected in series to the ac mains in circuit as shown. The bulb glows widh some brightness. How will the glow of the bulb change if (i) a dielectric slab is introduced between the plates of the capacitor, keeping resistance R to be the same; (ii) the resistance R is increased keeping the same capacitance ? A capacitor'C', 10. a variable resistor ffi ffi \rf,sqrr frqil eir d qq }rsn reil qrff t fu tdT{ $r sTqr et{ t oo" sT stur.Frrq, ir6r {68"{d s.F N." * qa qqri 6T er3{q mcor t r qk W tdqq q{ eTrivr + 4 nC t, fr Sr*i Milq 3;qi qfi$fud *i6q 2 cm cqr$ + aqf, B-{q +} qq I An electric dipole of length 2 cm, when placed with its axis making an angle of 60o with a uniform electric field, experiences a torque of 81[ Nm. Calculate the potential energy of the dipole, if it has a charge of + 4 nC. ll. qi gq-+iq qqpfr if mq r 'A' ork 'g' aulldls-? t t 'A' +t siliiqr*. Tq-whdaT w t go erfum t, q-qfu 'B' ftt w t qq1zfr fti qTfr wqrfrq I {+ qqrrl6t gqslq lgfrqT Tali+5c6ffi sxrqr Out of the two magnetic materials, 'A' has relative permeability slightly greater than unity while 'B' has less than unity. Identify the nature of the materials 'A' and 'B'. Will their susceptibilities be positive or negative ? 12. rsp-{o}-fi 6r W fu{rt fukq *i eq sqt *-fldqekf, | {iq}q it sdq dfuq lo gq rTvfrr sr Bqqtrr sTrafl{rd 6'it m.{i it t*,s }rfiRtsqr qror t r State the underlying principle of a cyclotron. Write briefly how this machine is used to accelerate charged particles to high energies. 13. a =ils6 frFrB +t qm,ar *a + a, sEqsqrqil +-(a' t{t + faq }. H{'rM + ffi t .r{ q;rdr I EnGrrT t r qfr slrT *1lqq } \rs-{uft r+rw .r{ 6q 'a' qt * do + qfrs{uT fud q.1 qem Wrm urd Ei vaffi kflr.it qr 2 r For a single slit of width "d', the first minimum of the interference paffern of monochromatic light of wavelength ?,, ;, *. 55lll2 l, a 1 occurs at an angle of ;. At the same angle of get a maximum for two narrow slits separated by a distance "a". Explain. 5 lP.T.O. 14. q{iqrrqizi +{,iqq +fdqsnq6 qg"ft fulqq I qt tcl tqrq frfuq r ewrqt tqq rrq qRqq feleq i[ p aqr e -drr eth-d iifwrfut *l qeqriqq r qs ritqq +fuq TTFrtrFT HR"ft r A B Write the truth table for the combination of the gates shown. Name the gates used. Identify the logic gates marked 'P' and 'Q' in the given circuit. Write the truth table for the combination. A B ts. ffi dd{ sil{ ffi ten orr *t vqn furd t dkd t*qr qE[6, de-qrrffi T{'thd. onorqkd5k*ifuq "Fr rn;r orFr+.drn, "ilc tiil ffir,rtdq tt t ffi I gq dit til g.qi sq &ft ? oTqi srt+t rrqr I A proton and an alpha particle are accelerated through the same potential. Which one of the two has (i) greater value of de-Broglie wavelength associated with it and (ii) less kinetic energy. Give reasons to justiff your answer. 16. : 2 x t03i Nlc HRr qffi fuqr.rqr t r qs qid Sss wffi ftt aro *ifrq 'il zO cm 5!ilt +ert * ss qrq-{ t rJ-{fir t fuq-sr ilaT y-z ?16 }'ITqrf,{ t r qk ffi crEr !i*-srl-{ frqd qir s} B x-srtr t 30'ql 6hiur E-{tq, A EHt : qri t.IGri qrd.rrw EFt rlFt wr Etrn ? Given a uniform electric field B 2 x tOl i N/C, find the flux of this field through a square of side 20 cm, whose plane is parallel to the y-z plane. What would be the flux through the same square, if the plane makes an angle of 30" with the x-axis ? 55/u2 17. ffiFfrqq State 1 8. (i) tdfuq {ietq I ii qrqr dfrqtrt fuq yqn qrq{irrd fl*.s Kirchhoff s rules. Explain briefly how these rules are t r justified' ffiAs{ERr 6.0 x 10la Hz errgfusrqq-qufrqErmsil=ttoqrrrqrt rwfravrk n6T qr;r 2.0 x t0-3 W t r eto Enr sft{il{ qfr t-#'s 3-d$kd sHit +1 {qr or silcFeFI *1leq t (ii) ffi (i) Monochromatic light of frequency 6.0 frq rrg ntrr$ {qm yB T{ oTrqfud frfu-tuit st d-{dr kd{ur *i q{ii qrf,r qrs dfrg I power emitted is 2.0 x *r u-*ru *qf, erRr + +q lOla Hz is produced by a laser. The x l0-3 W. Estimate the number of photons emitted per second on an average by the source. (ii) Draw a plot showing the variation of phrtoelectric current versus the intensity of incident radiation on a given photosensitive surface. re. (a) (b) qm md {Frcwg sq it sT qftqefrq Fr+q frfuq I dd qqn{ fuqrtieft {i*{r{s Sr der S, fu { Efliq 3r{sr{ !ts-{qiI slt e{fr ETRI "I" rffi ddql sr t E{r+ {{tfisi- B tr5^rdllt-d rrqrr mqrt *. qi * uq{ ftTqt t Etfr t, qi qrcfr {idflqs El*-{ fist erqr e t er6{ eTrfi s2 t {idkd tnqr ffi t I rK *tor nqr (iD 1iTfi fq{n{rd+iflqq qfr q+Ei frsH * {HFt tjIRI6(I" fuqtd tfln if vqnffi qfr {f,r$ dq-$ dEzi +1 {qr n, er{{ ffi tq- cTer ", t, d {i) w TiT gq-+iq t* +r qRqrur sk t nz ssfit2 gqtkr ait lP.T.O. (a) (b) State Ampere's circuital law, expressing it in the integral form. Two long coaxial insulated solenoids, S, and S, of equal lengths are wound one over the other as shown in the figure. A steady current "I" flow through the inner solenoid S, to the other end B, which is connected to the outer solenoid S, through which the same current "I" flows in the opposite direction so as to come out at end A. If n, and n2 are the number of turns per unit length, find the magnitude and direction of the net magnetic field at a point (i) inside on the axis and (ii) outside the combined system. I n2 20. +.qT HTq r?Tr t I turns q{ +{frq orcgtfi trt errErfr o-{i + frq rrtEl-fi q{qruJ qrvm *ufr +TdA v(Fr tss B-qt dsn qrqr ffi tz.q eV * {@.{ K{il6rsifsfl 6ti ? ffi +T6d w{q Eht {w mr sqqt r fl*qr ilr,'r*{ qftqiild +ifuq t A 12.9 eY beam of electrons is used to bombard gaseous hydrogen at room temperature. Upto which energy level the hydrogen atoms would be excited ? Calculate the wavelength of the first member of Paschen series and first member Balmer series. 2t. (a) ffi rtgff qeqqrfi fl-{r i}ihq der rsrs ilqii*.f, r+rvr fl+rur ento dlqq qfrkq fr*-u-dq $ of w q+qr Evrfi + fuq r t (b) ffi{gfiqmqrf t rik*,rERrrfl*T oTrqf{ s rvq HnrEdr=Tgm orrof+ zo qq rrq rrqr; qeq-qvfr si I qflr{vem 3fk itf,sr +dq *t frf{-dd sislsd t*qr niqm (fr t4 cm r qk Hs Ermil + frq srekrr Xt zo cm d di irfir{rrr st{ ffi t iksr ftt st-+-s Et qfir-sfdn dfi{q 55nt2 I (a) Draw a labelled ray diagram showing the formation of a final image by a compound microscope at least distance of distinct vision. (b) The total magnification produced by a compound microscope is 20. The magnification produced by the eye piece is 5. The microscope is focussed on a certain object. The distance between the objective and eyepiece is observed to be 14 cm. If least distance of distinct vision is 20 cm, calculate the focal length of the objective and the eye piece. 22. fi{qfrfud tsw{fuq : (a) vt +{d-gq-*iq mirii or il-q frfiqq fu{sr swtr $-s frk{d }rsr + affif *. sq-qn itfrqfuqrqrort (b) nrkrqqu-s(.T elz + rg+or enqfu-qrrulmfuq yfrS q{ Tf,d silt't-{ qrn qlrq t *t w-rfrkn *- fdq erfl< qaiqwt } I (c) ffi Vsaw sTrqtrd AW gqsiq nt it rn sr<iffi {+'r et rlrfl Egd sq Fii e}-fr t Z Answer the following : (a) Name the em waves which are used for the treatment of certain forms of cancer. Write their frequency range. (b) (c) 23. Thin ozone layer on top of stratosphere is crucial for human survival. Why ? Why is the amount of the momentum transferred by the em waves incident on the surface so small ? ffi +qr{e sqn xII *1 .rut, gitilr +) qq ?rdtrrd W{r t*.6s*fim+ erqi rrsn *t um +} qrf,r-fwdr t+qr r Bsi sTqi m.qfr si tflrq .rt +1 qtqqT +tr t, d ssi gs+r q{ sil{ Td flqflqrq sr $fr*lrr ]rqrq t6qr t*. E{+ tsr *.{+ FIr EI i{ciRrd ri*a scrq ffi ss* Rl ti qror-fqor ost uoq-a d.rg (l) ffi (3) fi : sTrdrfr 6ffifr d r1-*tqd m.Errl ERT ivur-zrd{ p{rfrf, $FII Er EI erkqrr*.fu{ trfl-{ d Tsm t ? (2) *i + fuq sr fl{frr *ttV+" + fo.q { 6t r-qfrffi flmqr r qRqr r*.fued 3wftiq dfif nkd *1 qr Hs-ft q+{r Enr 20 m *qr$ {{r.sr 3{F5FH s1tqq I $* 6t B-qr : 6400 km) sffii qnT-frnT +1+qqT +ffi ffi t, When Sunita, a class XII student, came to know that her parents are planning to rent out the top floor of their house to a mobile company she protested. She tried hard to convince her parents that this move would be a health hazard. Ultimately her parents agreed : (1) In what way can the setting up of transmission tower by a mobile company in a residential colony prove to be injurious to health ? (2) (3) By objecting to this move of her parents, what value did Sunita display ? Estimate the range of e.m. waves which can be transmitted by an antenna of height 20 m. (Given radius of the earth:6400 km) 55t112 lP.T.O. 24. ffiqttFflqifrc{* t.o rnnd dK"Frqftrnq 1: o t rqo*oft*qitffi s v+1ffi st{ s o + qftrftrn t {q}fud t r ss Hqfro. td 61 emf fuil'ka qitqq S oo cm T{ {iuffi lqgv-flT *-ror t r A potentiometer wire of length 1.0 m has a resistance of l5 O. It is connected to a 5 V battery in series with a resistance of 5 O. Determine the emf of the primary cell which gives a balance point at 60 cm. 25 . (a) iHrtl+ze errf,r *. frqq + fuq Eisl-.F, N : No e-)'t Edq *ifuq (b) (i) (iD (a) rftnrirrosq fr ?i.r" ++a (p*) nfi{+iq ufsqr sr sdq fr *1Hq Es HzI * w-qn ErT {lFlm- ?fo" Deduce the expression, N (b) (i) : qrq *1 qfffir t *] qm +iHq | {q flir +t Ao t * {Er {rkrt srerqr {qrTrfu+. ? N0 e-xt, for the law of radioactive decay. Write symbolically the process expressing the B+ decay of lft',fa. Atso write the basic nuclear process underlying this decay. 26. (a) (b) (iD Is the nucleus formed in the decay of the nucleus ?fon * isotope or isobar ? t st ffi r srgs eTltq srqTr(,r q{"r + ge ertr + q-fRyr rcr st-{ "t$Ehqqa sor?rf,r t gs-or qftkrq qrqt q{t{q I arrGrrT siiqqtr eTrcf{ \rs-sqH eit rfr t t ffi er+n-o q{'r + qra-fi ys sT kqf,r e{Iut qFI ffi oTqrr<{fr q-{-i t q{ .FIt uqq qgrn ? qrcqt *1kq aoflEqr rtqr t I Eqtn ffi frq qn dfrq t (a) A mobile phone lies along the principal axis of a concave mirror. Show, with the help of a suitable diagram, the formation of its image. Explain why magnification is not uniform. (b) Suppose the lower half of the concave mirror's reflecting surface is covered an opaque material. What effect this Explain. 55fit2 10 will with have on the image of the object ? 27. (a) ffi oil-afrrd dfeq {rilR-{ qEsr {qrfu it qh g+rt enqd-{ qsrnm rmt + frq ais*,'srq r (b) ffivqffi{vpsr {qriu+$-iKtqqd + or{kyr ffi sTr&[r q qia "ilqH p t st.rfr v-tri n foqr.rqr anr{ vro rw o{rirdrtrr(e a b c d a eilqq t ++++++.+ rlrlttl qeltrt (a) forfr qqr:nr qtrsr {qrfu FRr+t qflr+r *,r eias-d A f,sTr qiffirsit ++q yrsr d t, s1 qri{-dr *. frq aiqq. E-trq qiflqq r (b) Rr derT R2 fi-qoif + qi o{-afrH .ilf,iq qe-{it +} qq ffi qrco iTr-{ 6RT i{qit{d lsqr qrm t ni t mqsr' qr ipn e, onivr erfuo m-r tA t r w qre-*t s1 trqrcTt + r<i { ET+yd.q (a) s{r+{r r{Fii sr q-{qr?T 66 +iFq r Obtain the expression for the energy stored per unit volume in a charged parallel plate capacitor. (b) The electric field inside a parallel plate capacitor is E. Find the amount of work done in moving a charge q over a closed rectangular loop a b c d a. +++++++ ttttlll OR (a) Derive the expression for the capacitance of a parallel plate capacitor having plate area A and plate separation d. (b) Two charged spherical conductors of radii R, and R, when connected by a conducting wire acquire charges g1 and g2 respectively. Find the ratio of their surface charge densities in terms of theu radii. 55ilt2 11 lP.T.O. 28. (a) t*'S t+ vre u-dq (s{erEr fuqre.mg qr quh dfuq* qe qflidr tflm.t*.$ T.sfr d nftd f{qf, qrFF qrT (emf) d q-** rrta {s s-f,r-{ *fr t to qo QS qra 6fl=t qri qr u-qrs or$ t qi gt Ef,r=r q.d qrd Tq-dq rffi.Rr t qkqdq or Rr *t r (b) ffi t, t fun"ii dr q{ii *.foqqrq.dlqq , (D nir*. furrfir '*rdriq L grq-+iq TFI.RI sfu qmr rdr|cd qrr il Frrf,{ Ek Ei t rfi r firafufun *+q (iD ika emf Slr aYAt * dq (iii) {iftn gqiq fiFlfrq u.qt sfu qrr + *q slslEtr (a) Ao werdt or quh u.rtr gq ffi ac qfux *.r qtr Tr sTi{q Eifuq I EsS *.tffi fu r< oT ri$q ii cdq 6ikq r ffi Tqsiq qh fr q'ir +,d qrd ffi W gnrt anrqko (D 1qdqwFR[, (iD trffiTdT emf dPrr ekqrq ++q kqrq *i qqii *.frqurwdlqq (b) ac (a) Describe a simple experiment (or activity) ifq *.qrq qtilfik rfrsr +sq+'r t { qtr$-s-fr *t enwqoar wit tt-tr t z to show that the polarity of emf induced in a coil is always such that it tends to produce a current which opposes the change of magnetic flux that produces it. (b) The current flowing through an inductor of self inductance increasing. Plot a graph showing the variation (D Magnetic flux versus the current (iD Induced emf versus dl/dt (iii) Magnetic potential energy stored versus the current. OR ssfit2 of 12 L is continuously (a) Draw a schematic sketch of an ac generator describing its basic elements. State briefly its working principle. Show (i) (ii) a plot of variation of Magnetic flux and Alternating emf versus time generated by a loop of wire rotating in a magnetic field. (b) zs. (a) Why is choke coil needed in the use of fluorescent tubes with ac mains ? p-n riPr *ifrqtror$ arrcrrr (b) ffii ii {Fqfud qfsqrcri sr {etq if cdq dtqq sil{ $r+1 $ sq elr 6T frqiur t+s q-src+f,r t t qoqvrtqqfuffi *t 1i1 srrJt(frrs qus (iD qq-qffirs'Er{rs rt v-r s{Frffi{erofl*q u-srqrEil frq+-{q it Ea srFrerqrnrr+} q.r sr+'r floq vq.r stst t r errqrcoqfrqq oTrttit sor+or Fq p-n riFr +tdq t*qqri flsqr qrdr t t t ? tt (a) ffi qrFqs{+d-{ q,,st ++q st* qrrq $qqrfi-K{* srrcIrv{fuffi +1kq (b) ffi <iks{*t fu{ ronqrqkd o'{h{f;nq effi Tr itarqr qror tz (c) slrnwrs qfrqE sTrtq +t {6rirdT t qrf{ +tfuq fu cB kqq it Bt$ n-p-n qiflsne{, r t*-s q-fl-{ frfuq (a) State ffi Eg qr q-*tq firn{ft qt dr sr }rq*{ qror t I ac qRr HleT + laq W r briefly the processes involved in the formation of p-n junction explaining clearly how the depletion region is formed. (b) Using the necessary circuit diagrams, show how the p-n junction are obtained in (D Forward biasing (iD Reverse biasing V-I How are these characteristics made use of in rectification ssnt2 13 characteristics of a ? lP.T.O. (a) Differentiate between three segments of a transistor on the basis of their size and level of doping. (b) (c) How is a transistor biased to be in active state ? With the help of necessary circuit diagram, describe briefly how n-p-n transistor in CE configuration amplifies a small sinusoidal input voltage. Write the expression for the ac current gain. 30. (a) (i) 'i s;* \r*-dufr u-qrvr *f, fr-# qnq{frq (ii) Ei s*i t' {s*r t s*kd r+ru efi fr+i }r+fi irt efl-ilrt a aw erqfu ro t ffi kgw silqniqur *-tfr t d cos(rrrt + O), T6i +kqeqq-6urq*1kq (b) reT q.r vsq r s-dRi*6 q-{Rr *it y2: H qftffirq O I qfrg+ rrrii *.onq fusrm +it * +q $ett<R yt: d cos ort rlefl t d, A {s k q{ qne'nfr *{dr r mt t ffi it G + trdrr, 1., ilt1}{ + \'s-{"f y"FtYT c5t sqqtrr t+qr .rqr 'irr S Et$rfr f+g w wi w qqrtr{ x/3 fu , fus q{ qerf,{ 1 }, r+rvr qi *f,dr K q:rs't r ffi |, u-*rvr *t frildr arn dfqq r qsrdlt (a) wTff oTnne +1 {fl?rdT t qe H fiKfrm floqr qr {s-dr t fo. qqfrf, u-srvr ffi qlt{-{st Uqri w qfqn E} qrnr t (b) s1-$ Etdr r{ s{rqfuf, t r sq5ffi t*.{rr o{iq si +oq{i-{qt* qs e-d{rggt Trrcffi-d utrTvl, qlq p: tan i, t, d qfr' qf+a stqfriT IFFRT 5_q sdFraT t ? t, .rfr p *iq ffi sT qrg fti-q-atg rf,{rgs +qttqr (a) (D 'Two independent gTq-{f,{is-HelT i, qer *iu monochromatic sources t r of light cannot produce a sustained interference pattem'. Give reason. (ii) Light waves each of amplitude "d' and frequency "{D", emanating from two coherent light sources superpose at a point. If the displacements due to these waves is given by yr : a cos rot ardyz: a cos(rot + Q) where Q is the phase difference between the two, obtain the expression for the resultant intensity at the point. 55nt2 t4 (b) In Young's double slit experiment, using monochromatic light of wavelength 1,, the intensity of light at a point on the screen where path difference is 1", is K units. Find out the intensity of light at a point where path difference is l,/3. OR (a) How does one demonstrate, using a suitable diagram, that unpolarised light when passed through a Polaroid gets polarised ? (b) A beam of unpolarised light is incident on a glass-air interface. Show, using a suitable ray diagram, that light reflected from the interface is totally polarised, when p : tan is, where p is the refractive index of glass with respect to air and is the Brewster's angle. 55fi12 15 i,

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