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CBSE Class XII 2014 : PHYSICS

15 pages, 91 questions, 50 questions with responses, 62 total responses,    0    0
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H$moS> Z . Series OSR Code No. amob Z . 55/1 narjmWu H$moS >H$mo C ma-nwp VH$m Ho$ _wI-n >na Ad ` {bIo & Roll No. Candidates must write the Code on the title page of the answer-book. H $n`m Om M H$a b| {H$ Bg Z-n _o _w{ V n > 15 h & Z-n _| Xm{hZo hmW H$s Amoa {XE JE H$moS >Z ~a H$mo N>m C ma -nwp VH$m Ho$ _wI-n > na {bI| & H $n`m Om M H$a b| {H$ Bg Z-n _| >30 Z h & H $n`m Z H$m C ma {bIZm ew $ H$aZo go nhbo, Z H$m H $_m H$ Ad ` {bI| & Bg Z-n H$mo n T>Zo Ho$ {bE 15 {_ZQ >H$m g_` {X`m J`m h & Z-n H$m {dVaU nydm _| 10.15 ~Oo {H$`m OmEJm & 10.15 ~Oo go 10.30 ~Oo VH$ N>m Ho$db Z-n H$mo n T>|Jo Am a Bg Ad{Y Ho$ Xm amZ do C ma-nwp VH$m na H$moB C ma Zht {bI|Jo & 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. ^m {VH$ {dkmZ (g mp VH$) PHYSICS (Theory) {ZYm [aV g_` : 3 K Q>o A{YH$V_ A H$ : 70 Time allowed : 3 hours 55/1 Maximum Marks : 70 1 P.T.O. gm_m ` {ZX}e : (i) g^r Z A{Zdm` h & (ii) Bg Z-n _| Hw$b 30 Z h & Z 1 go 8 VH$ Ho$ Z A{V-bKwC mar` Z h Am a `oH$ EH$ A H$ H$m h & (iii) Z 9 go 18 _| `oH$ Z Xmo A H$ H$m h , Z 19 go 27 _| `oH$ Z VrZ A H$ H$m h Am a Z 28 go 30 _| `oH$ Z nm M A H$ H$m h & (iv) VrZ A H$m| dmbo Zm| _| go EH$ _y `naH$ Z h & (v) Z-n _| g_J na H$moB {dH$ n Zht h & VWm{n, Xmo A H$m| dmbo EH$ Z _|, VrZ A H$m| dmbo EH$ Z _| Am a nm M A H$m| dmbo VrZm| Zm| _| Am V[aH$ M`Z XmZ {H$`m J`m h & Eogo Zm| _| AmnH$mo {XE JE M`Z _| go Ho$db EH$ Z hr H$aZm h & (vi) H $bHw$boQ>a Ho$ Cn`moJ H$s AZw_{V Zht h & VWm{n `{X Amd `H$ hmo Vmo Amn bKwJUH$s` gmaUr H$m `moJ H$a gH$Vo h & (vii) Ohm Amd `H$ hmo Amn {Z Z{b{IV ^m {VH$ {Z`Vm H$m| Ho$ _mZm| H$m Cn`moJ H$a gH$Vo h : c = 3 108 m/s h = 6.63 10 34 Js e = 1.6 10 19 C o = 4 10 7 T mA 1 1 = 9 109 N m2 C 2 4 o me = 9.1 10 31 kg General Instructions : (i) All questions are compulsory. (ii) There are 30 questions in total. Questions No. 1 to 8 are very short answer type questions and carry one mark each. (iii) Questions No. 9 to 18 carry two marks each, questions 19 to 27 carry three marks each and questions 28 to 30 carry five marks each. (iv) One of the questions carrying three marks weightage is value based question. 55/1 2 (v) There is no overall choice. However, an internal choice has been provided in one question of two marks, one question of three marks and all three questions of five marks each weightage. You have to attempt only one of the choices in such questions. (vi) Use of calculators is not permitted. However, you may use log tables if necessary. (vii) You may use the following values of physical constants wherever necessary : c = 3 108 m/s h = 6.63 10 34 Js e = 1.6 10 19 C o = 4 10 7 T mA 1 1 = 9 109 N m2 C 2 4 o me = 9.1 10 31 kg 1. AZ V b ~mB Ho$ Xmo Ymamdmhr g_m Va MmbH$m| Ho$ ~rM ~b H$s g H$ nZm H$m Cn`moJ H$aVo h E EH$ Eop n`a Ymam H$s n[a^mfm Xr{OE & 1 Using the concept of force between two infinitely long parallel current carrying conductors, define one ampere of current. 2. 5 1019 Hz Amd { m H$s Va J {d wV -Mw ~H$s` no Q >_ Ho$ {H$g ^mJ go g ~ Y aIVr h ? 1 To which part of the electromagnetic spectrum does a wave of frequency 5 1019 Hz belong ? 3. Xmo g_mZ J oX| {OZ na q Hy$bm _ Ho$ g_mZ YZmdoe h g_mZ b ~mB H$s Xmo {d wV amoYr S>mo[a`m| go {Zb {~V h & BZHo$ ~rM bJZo dmbo ~b na `m ^md hmoJm O~ BZ XmoZm| J oXm| Ho$ ~rM H$moB bmp Q>H$ H$s MmXa aI Xr OmE ? 1 Two equal balls having equal positive charge q coulombs are suspended by two insulating strings of equal length. What would be the effect on the force when a plastic sheet is inserted between the two ? 55/1 3 P.T.O. 4. H$me Ho$ \$moQ>m Z {M U Ho$ AmYma na {d{H$aU H$s Vrd Vm H$mo n[a^m{fV H$s{OE & BgH$m Eg.AmB . (S.I.) _m H$ {b{IE & 1 Define intensity of radiation on the basis of photon picture of light. Write its S.I. unit. 5. {H$gr Vma _| B go A {Xem H$s Amoa dm{hV {d wV Ymam KQ> ahr h & {M _| Xem E AZwgma Bg Vma Ho$ D$na p WV {H$gr YmVw Ho$ byn (nme) _| o[aV Ymam H$s {Xem kmV H$s{OE & 1 The electric current flowing in a wire in the direction from B to A is decreasing. Find out the direction of the induced current in the metallic loop kept above the wire as shown. 6. Zm{^H$s` -j` _| `y{Q >Zm| H$m g gyMZ m`mo{JH$ $n _| H${R>Z `m| nm`m OmVm h ? 1 Why is it found experimentally difficult to detect neutrinos in nuclear -decay ? 7. d.c. dmo Q>Vm H$s VwbZm _| H$maU Xr{OE & a.c. dmo Q>Vm Ho$ Cn`moJ H$mo mW{_H$Vm `m| Xr OmVr h ? Xmo 1 Why is the use of a.c. voltage preferred over d.c. voltage ? Give two reasons. 8. 1.25 AndV Zm H$ Ho$ nmaXeu nXmW go ~Zo {H$gr C^`mo mb b|g H$mo 1.33 AndV Zm H$ Ho$ Ob _| Sw>~mo`m J`m h & `m `h b|g A{^gmar Ho$ $n _ o `dhma H$aoJm AWdm Angmar Ho$ $n _| ? H$maU Xr{OE & A biconvex lens made of a transparent material of refractive index 1.25 is immersed in water of refractive index 1.33. Will the lens behave as a converging or a diverging lens ? Give reason. 55/1 4 1 9. na_mUw Ho$ aXa\$moS> _m S>b H$m Cn`moJ H$aVo h E hmBS >moOZ na_mUw _| Bbo Q >m Z H$s Hw$b D$Om Ho$ {bE ` OH$ `w n H$s{OE & Bbo Q >m Z H$s Hw$b D$Om G$Um _H$ hmoZo H$m `m AW h ? 2 AWdm ~moa Ho$ na_mUw _m S>b Ho$ A{^J hrVm| H$m Cn`moJ H$aHo$ Bbo Q >m Z H$s ndt H$jm H$s { `m Ho$ {bE ` OH$ `w n H$s{OE & Bg H$ma ~moa H$s { `m Ho$ {bE ` OH$ m V H$s{OE & 2 Using Rutherford model of the atom, derive the expression for the total energy of the electron in hydrogen atom. What is the significance of total negative energy possessed by the electron ? OR Using Bohr s postulates of the atomic model, derive the expression for radius of nth electron orbit. Hence obtain the expression for Bohr s radius. 10. Ym[aVm C Ho$ {H$gr g_m Va n{ >H$m g Ym[a H$mo {d^d V VH$ Amdo{eV {H$`m J`m & BgHo$ n MmV Bgo g_mZ Ym[aVm Ho$ {H$gr A ` g Ym[a , Omo Amdo{eV Zht h , go g `mo{OV {H$`m OmVm h & g `w $ {ZH$m` _| g {MV D$Om Am a Ama ^ _| EH$b g Ym[a _| g {MV D$Om H$m AZwnmV kmV H$s{OE & 2 A parallel plate capacitor of capacitance C is charged to a potential V. It is then connected to another uncharged capacitor having the same capacitance. Find out the ratio of the energy stored in the combined system to that stored initially in the single capacitor. 11. {H$gr g_m Va n{ >H$m g Ym[a Ho$ Amdo{eV hmoZo Ho$ H$aU na {dMma H$aVo h E `h Xem BE {H$ {d WmnZ Ymam Ho$ H$maU nX H$mo gp _{bV H$aZo Ho$ {bE Eop n`a Ho$ n[anWr` {Z`_ H$mo {H$g H$ma `mnH$ ~ZmZo H$s Amd `H$Vm hmoVr h & 2 Considering the case of a parallel plate capacitor being charged, show how one is required to generalize Ampere s circuital law to include the term due to displacement current. 55/1 5 P.T.O. 12. {H$gr gob {OgH$m {d wV -dmhH$ ~b (emf) E VWm Am V[aH$ {VamoY r h , {H$gr Ma {VamoYH$ R Ho$ {gam o go g `mo{OV {H$`m J`m h & gob H$s Q>{_ Zb dmo Q>Vm V Am a Ymam I Ho$ ~rM {dMaU H$mo Xem Zo Ho$ {bE J m \$ It{ME & Bg J m \$ H$m Cn`moJ H$aHo$ `h Xem BE {H$ gob H$m {d wV -dmhH$ ~b (emf) Am a BgHo$ Am V[aH$ {VamoY H$m {ZYm aU {H$g H$ma {H$`m Om gH$Vm h & 2 A cell of emf E and internal resistance r is connected across a variable resistor R . Plot a graph showing variation of terminal voltage V of the cell versus the current I . Using the plot, show how the emf of the cell and its internal resistance can be determined. 13. n[anW AmaoI H$s ghm`Vm go {H$gr H$aZo H$s `m `m H$s{OE & p-n g {Y S>m`moS> Ho$ AY -Va J {X Q>H$mar Ho$ $n _| H$m` 2 Explain, with the help of a circuit diagram, the working of a p-n junction diode as a half-wave rectifier. 14. {H$gr Vm ~o Ho$ Vma, {OgH$s AZw W-H$mQ> H$m jo \$b 1.0 10 7 m2 h VWm {Oggo 1.5 A Ymam dm{hV hmo ahr h , _| MmbZ Bbo Q >m Zm| H$s Am gV Andmh Mmb H$m AmH$bZ H$s{OE & `h _m{ZE {H$ MmbZ Bbo Q >m Zm| H$m KZ d 9 1028 m 3 h & 2 Estimate the average drift speed of conduction electrons in a copper wire of cross-sectional area 1.0 10 7 m2 carrying a current of 1.5 A. Assume the density of conduction electrons to be 9 1028 m 3. 15. 55/1 {H$gr g_{ ~mh g_H$moU { _ ABC Ho$ \$bH$ AB na Xem E AZwgma EH$dUu H$me H$s Xmo {H$aU| A{^b ~dV AmnVZ H$aVr h & H$m M Ho$ { _ Ho$ AndV Zm H$ {H$aUm| 1 d 2 Ho$ {bE H $_e: 1.35 Am a 1.45 h & BZ {H$aUm| H$m { _ _| doe H$aZo Ho$ n MmV H$m nW Amao{IV H$s{OE & 6 2 Two monochromatic rays of light are incident normally on the face AB of an isosceles right-angled prism ABC. The refractive indices of the glass prism for the two rays 1 and 2 are respectively 1.35 and 1.45. Trace the path of these rays after entering through the prism. 16. g Mma Umbr _| {Z Z{b{IV Ho$ H$m` {b{IE (i) Q >m gS `yga (ii) nwZamdV H$ : 2 Write the functions of the following in communication systems : (i) (ii) 17. Transducer Repeater (i) AZwMw ~H$s` nXmW Ed (ii) {VMw ~H$s` nXmW H$s Cnp W{V _| Mw ~H$s` jo aoImAm| H$m `dhma AmaoI ItMH$a Xem BE & Bg {d^oXZH$mar bjU H$s `m `m {H$g H$ma H$s OmVr h ? 2 Show diagrammatically the behaviour of magnetic field lines in the presence of (i) paramagnetic and (ii) diamagnetic substances. How does one explain this distinguishing feature ? 18. CE {d `mg _| n-p-n Q >m { O Q>a dY H$ H$m n[anW AmaoI It{ME & {H$g Ad Wm _| `h Q >m { O Q>a dY H$ Ho$ $n _| H$m` H$aVm h ? 2 Draw a circuit diagram of n-p-n transistor amplifier in CE configuration. Under what condition does the transistor act as an amplifier ? 55/1 7 P.T.O. 19. (a) Y wdU H$s n[aKQ>Zm H$m Cn`moJ H$aVo h E `h Xem BE {H$ H$me H$s AZw W H ${V H$m {ZXe Z {H$g H$ma {H$`m Om gH$Vm h & (b) Xmo nmoboam BS>m| P1 VWm P2 H$mo Bg H$ma aIm J`m h {H$ BZHo$ nm[aV-Aj EH$-X gao Ho$ b ~dV hm| & Vrd Vm Io H$m AY w{dV H$me P1 na Amn{VV h & {H$gr Vrgao nmoboam BS> P3 H$mo P1 Am a P2 Ho$ ~rM Bg H$ma aIm J`m h {H$ BgH$m nm[aV-Aj P1 Ho$ nm[aV-Aj go 30 H$m H$moU ~ZmE & P1, P2 Am a P3 go Jw OaZo 3 dmbo H$me H$s Vrd Vm {ZYm [aV H$s{OE & (a) Using the phenomenon of polarisation, show how transverse nature of light can be demonstrated. (b) Two polaroids P1 and P2 are placed with their pass axes perpendicular to each other. Unpolarised light of intensity Io is incident on P1. A third polaroid P3 is kept in between P1 and P2 such that its pass axis makes an angle of 30 with that of P1. Determine the intensity of light transmitted through P1, P2 and P3. 20. Xmo Hw$ S>{b`m| Ho$ ~rM "A `mo ` oaH$ d' nX H$s n[a^mfm {b{IE & Xmo b ~o g_mj gmoboZm BS>m|, {OZ_| `oH$ H$s b ~mB l VWm { `mE r1 Am a r2 (r2 >> r1) h , Ho$ `wJb Ho$ A `mo ` oaH$ d Ho$ {bE ` OH$ m H$s{OE & BZ Xmo gmoboZm BS>m| _| bnoQ>m| H$s Hw$b g `m H $_e: N1 Am a N2 h & 3 Define the term mutual inductance between the two coils. Obtain the expression for mutual inductance of a pair of long coaxial solenoids each of length l and radii r1 and r2 (r2 >> r1). Total number of turns in the two solenoids are N1 and N2 respectively. 55/1 8 21. {Z Z{b{IV Ho$ C ma Xr{OE : 3 (a) _rQ>a goVw _| {VamoYH$m| Ho$ ~rM g `moOZm| H$mo H$m na H$s _moQ>r n >r H$m `m| ~Zm`m OmVm h ? (b) _rQ>a goVw Ho$ Vma na gm_m `V: g VwbZ {~ X H$mo _ ` _| m H$aZo H$mo mW{_H$Vm `mo Xr OmVr h ? (c) _rQ>a goVw Ho$ Vma Ho$ {bE {H$g nXmW H$m Cn`moJ {H$`m OmVm h Am a `m| ? AWdm {M _| Xem E AZwgma Hw$b {VamoY Ro R H$m H$moB {VamoY {d^d_mnr go Ymam boVm h & {d^d_mnr H$m h & {d^d_mnr H$mo V g nH $ {d^d_mnr Vma Ho$ _ ` _| h , V~ dmo Q>Vm H$s Amny{V H$s OmVr h & O~ gnu R Ho$ {gam| na dmo Q>Vm Ho$ {bE ` OH$ `w n 3 H$s{OE & Answer the following : (a) Why are the connections between the resistors in a meter bridge made of thick copper strips ? (b) Why is it generally preferred to obtain the balance point in the middle of the meter bridge wire ? (c) Which material is used for the meter bridge wire and why ? OR 55/1 9 P.T.O. A resistance of R draws current from a potentiometer as shown in the figure. The potentiometer has a total resistance Ro . A voltage V is supplied to the potentiometer. Derive an expression for the voltage across R when the sliding contact is in the middle of the potentiometer. 22. {H$gr 20 cm \$moH$g X ar Ho$ C mb b|g H$mo 20 cm dH $Vm { `m Ho$ C mb Xn U Ho$ g_mj aIm J`m h & XmoZm| Ho$ ~rM H$s X ar 15 cm h & H$moB {~ Xw{H$V {~ ~ C mb b|g Ho$ gm_Zo 60 cm X ar na aIm h & Bg g `moOZ mam {V{~ ~ ~ZZm Xem Zo Ho$ {bE {H$aU AmaoI It{ME & Bg {V{~ ~ H$s p W{V Am a H ${V {ZYm [aV H$s{OE & 3 A convex lens of focal length 20 cm is placed coaxially with a convex mirror of radius of curvature 20 cm. The two are kept at 15 cm from each other. A point object lies 60 cm in front of the convex lens. Draw a ray diagram to show the formation of the image by the combination. Determine the nature and position of the image formed. 23. {H$gr loUr LCR n[anW na H$moB dmo Q>Vm V = Vo sin t AZw `w $ H$s OmVr h & EH$ MH $ _ o Am gV j{`V e{ $ Ho$ {bE ` OH$ `w n H$s{OE & {H$g Ad Wm _ o (i) ` {n n[anW _| {d wV Ymam dm{hV hmo ahr h {\$a ^r e{ $-j` Zht hmoVm, (ii) n[anW _| A{YH$V_ e{ $-j` hmoVm h ? A voltage V = Vo sin t is applied to a series LCR circuit. Derive the expression for the average power dissipated over a cycle. Under what condition is (i) no power dissipated even though the current flows through the circuit, (ii) maximum power dissipated in the circuit ? 55/1 10 3 24. D$Om ~ S> AmaoIm| Ho$ AmYma na MmbH$m|, AY MmbH$m| Am a {d wV -amo{Y`m| Ho$ ~rM {H$ ht Xmo {d^oXZH$mar bjUm| H$mo {b{IE & Write any two distinguishing features between 3 conductors, semiconductors and insulators on the basis of energy band diagrams. 25. {nN>bo Hw$N> g_` go AmaVr AnZr ~hZ amYm H$s Hw$N> XmofnyU emar[aH$ J{V`m|, Ap WaVm Am a {H $`mH$bmnm| _| g_ d` _| H$_r H$m ojU H$a ahr Wr & dh `Xm -H$Xm Vrd {gaXX H$s {eH$m`V ^r H$aVr Wr & AmaVr Zo AnZo _mVm-{nVm go amYm H$s S>m Q>ar-Om M H$m gwPmd {X`m & S>m Q>a Zo amYm H$m JhZ narjU {H$`m Am a `h {ZXmZ {H$`m {H$ amYm ~ oZ-Q >`y_a go nr{ S>V h & (a) AmnHo$ AZwgma AmaVr Zo {H$Z _y `m| H$mo X{e V {H$`m ? (b) ao{S>`moAmBgmoQ>mon {H$g H$ma S>m Q>am| H$s ~ oZ-Q >`y_a H$m {ZXmZ H$aZo _| ghm`Vm H$aVo h ? 3 For the past some time, Aarti had been observing some erratic body movement, unsteadiness and lack of coordination in the activities of her sister Radha, who also used to complain of severe headache occasionally. Aarti suggested to her parents to get a medical check-up of Radha. The doctor thoroughly examined Radha and diagnosed that she has a brain tumour. (a) (b) 26. What, according to you, are the values displayed by Aarti ? How can radioisotopes help a doctor to diagnose brain tumour ? g Mma Ho$ Xmo _yb T> J ({dYmE ) {b{IE & Am`m_ _m Sw>bZ H$s {H $`m H$s `m `m H$s{OE & {H$gr `d Wm AmaoI H$mo ItMH$a `h Xem BE {H$ {H$gr `mdH $s` dmhH$ Va J na _m Sw>bH$ {g Zb Ho$ A `mamonU mam {H$g H$ma Am`m_ _m Sw>{bV {g Zb m {H$`m OmVm h & 3 Write two basic modes of communication. Explain the process of amplitude modulation. Draw a schematic sketch showing how amplitude modulated signal is obtained by superposing a modulating signal over a sinusoidal carrier wave. 55/1 11 P.T.O. 27. H$moB Bbo Q >m Z gy _Xeu 50 kV H$s dmo Q>Vm mam d[aV Bbo Q >m Zm| H$m Cn`moJ H$aVm h & Bbo Q >m Zm| go g ~ Xo-~m br Va JX ` {ZYm [aV H$s{OE & A ` H$maH$m|, O go Am {H$H$ maH$ Am{X H$mo g_mZ _mZVo h E, {H$gr Bbo Q >m Z gy _Xeu H$s {d^oXZ j_Vm H$s VwbZm {H$gr Eogo H$m{eH$ gy _Xeu {Og_| nrbo H$me H$m Cn`moJ hmoVm h , H $go H$s OmVr h ? 3 An electron microscope uses electrons accelerated by a voltage of 50 kV. Determine the de-Broglie wavelength associated with the electrons. Taking other factors, such as numerical aperture etc. to be same, how does the resolving power of an electron microscope compare with that of an optical microscope which uses yellow light ? 28. dm S>o J m \$ O{Z H$m Zm_m {H$V AmaoI It{ME & `h Xem Zo Ho$ {bE {H$, {H$g H$ma {H$gr ~ S>o Jmobo Ho$ ^rVa {H$gr Amdo{eV N>moQo Jmobo H$mo aIH$a ~ S>o Jmobo na {demb _m m _| Amdoe H$mo WmZm V[aV {H$`m Om gH$Vm h , Bg O{Z H$m H$m` H$mar {g m V {b{IE & Bg _erZ Ho$ Cn`moJ H$m C oI H$s{OE VWm BgH$s gr_mE ^r {b{IE & 5 AWdm (a) (b) 55/1 {H$gr EH$g_mZ {d wV -jo E H$s Cnp W{V _| [ Yw d AmKyU p dmbo {H$gr [ Y wd na H$m` H$aZo dmbo ~b-AmKyU Ho$ {bE ` OH$ `w n H$s{OE & {M _| Xem E AZwgma Xmo ImoIbo g Ho$ r Jmobm| S1 VWm S2 na {dMma H$s{OE {OZ na H $_e: 2Q VWm 4Q Amdoe n[a~ h & (i) BZgo Jw OaZo dmbo {d wV b g H$m AZwnmV kmV H$s{OE & (ii) `{X S1 Ho$ ^rVar WmZ _| dm`w Ho$ WmZ na namd wVm H$ r H$m H$moB _m `_ ^a {X`m OmE, Vmo Jmobo S1 go Jw OaZo dmbo {d wV b g _| `m n[adV Z hmoJm ? Amd `H$ ` OH$ `w n H$s{OE & 12 5 Draw a labelled diagram of Van de Graaff generator. State its working principle to show how by introducing a small charged sphere into a larger sphere, a large amount of charge can be transferred to the outer sphere. State the use of this machine and also point out its limitations. OR (a) Deduce the expression for the torque acting on a dipole of dipole moment p in the presence of a uniform electric field E . (b) Consider two hollow concentric spheres, S1 and S2, enclosing charges 2Q and 4Q respectively as shown in the figure. (i) Find out the ratio of the electric flux through them. (ii) How will the electric flux through the sphere S1 change if a medium of dielectric constant r is introduced in the space inside S1 in place of air ? Deduce the necessary expression. 29. (a) (b) (a) 55/1 ` J Ho$ [ {Par `moJ _|, g jon _| dU Z H$s{OE {H$ [ {Par Ho$ gm_Zo p WV nX o na M_H$sbr Am a H$mbr Ym[a`m (q\ $O) {H$g H$ma m H$s OmVr h & Bg H$ma q\ $O Mm S>mB Ho$ {bE ` OH$ m H$s{OE &$ ` J Ho$ [ {Par `moJ _| {Zp Z R> Am a C{ R> H$s Vrd VmAm| H$m AZwnmV 9 : 25 h & XmoZm| {Par`m| H$s Mm S>mB`m| H$m AZwnmV kmV H$s{OE & AWdm g jon _| dU Z H$s{OE {H$ {H$gr EH$dUu H$me moV mam Xr V {H$gr EH$b nVbr {Par Ho$ H$maU {H$gr nX o na {ddV Z n Q>Z {H$g H$ma m {H$`m OmVm h & Bg H$ma [ Vr`H$ C{ R> Am a [ Vr`H$ {Zp Z R> H$s H$moUr` Mm S>mB Ho$ {bE eV] m V H$s{OE & 13 5 P.T.O. (b) 2 10 6 m maH$ H$s EH$b {Par mam hmoZo dmbo {ddV Z H$m A ``Z H$aZo Ho$ {bE ~mar-~mar go gmo{S>`_ Ho$ H$me H$s 590 nm Am a 596 nm H$s Xmo Va JX `m o H$m Cn`moJ {H$`m J`m & {Par Am a nX} Ho$ ~rM H$s X ar 1.5 m h & XmoZm| H$aUm| _| m {ddV Z n Q>Zm o _| nhbo C{ R> H$s p W{V`m| Ho$ ~rM n WH$Z n[aH${bV H$s{OE & (a) In Young s double slit experiment, describe briefly how bright and dark fringes are obtained on the screen kept in front of a double slit. Hence obtain the expression for the fringe width. (b) 5 The ratio of the intensities at minima to the maxima in the Young s double slit experiment is 9 : 25. Find the ratio of the widths of the two slits. OR (a) (b) Two wavelengths of sodium light of 590 nm and 596 nm are used in turn to study the diffraction taking place at a single slit of aperture 2 10 6 m. The distance between the slit and the screen is 1.5 m. Calculate the separation between the positions of first maxima of the diffraction pattern obtained in the two cases. (a) Mw ~H$s` jo _| {H$gr Amdo{eV H$U H$s n[aH $_U Amd { m Ho$ {bE ` OH$ `w n H$s{OE Am a `h Xem BE {H$ `h Amd { m H$U Ho$ doJ AWdm CgH$s D$Om na {Z^ a Zht h & (b) 30. Describe briefly how a diffraction pattern is obtained on a screen due to a single narrow slit illuminated by a monochromatic source of light. Hence obtain the conditions for the angular width of secondary maxima and secondary minima. gmB bmoQ >m Z H$m `d Wm AmaoI It{ME & BgH$s g aMZm H$m Amd `H$ {d V V {ddaU XoVo h E `m `m H$s{OE {H$ Amdo{eV H$Um| H$mo d[aV H$aZo Ho$ {bE BgH$m Cn`moJ {H$g H$ma {H$`m OmVm h & AWdm (a) 55/1 Mb Hw$ S>br J doZmo_rQ>a H$m Zm_m {H$V AmaoI It{ME & BgHo$ {g m V Am a H$m` Umbr H$m g jon _| dU Z H$s{OE & 14 5 (b) {Z Z{b{IV Ho$ C ma Xr{OE : (i) J doZmo_rQ>a H$s Hw$ S>br Ho$ ~rM Z_ bmoho Ho$ ~obZmH$ma H $moS> H$mo aIZm `m| Amd `H$ h ? (ii) {H$gr J doZmo_rQ>a H$s Ymam gwJ m{hVm _| d { H$aZo H$m Vm n` `h Zht h {H$ CgH$s dmo Q>Vm gwJ m{hVm _| ^r A{Zdm` V d { hmo OmEJr & H$maU XoVo h E `m `m H$s{OE & (a) Deduce an expression for the frequency of revolution of a charged particle in a magnetic field and show that it is independent of velocity or energy of the particle. (b) 5 Draw a schematic sketch of a cyclotron. Explain, giving the essential details of its construction, how it is used to accelerate the charged particles. OR (a) Draw a labelled diagram of a moving coil galvanometer. Describe briefly its principle and working. (b) Answer the following : (i) Why is it necessary to introduce a cylindrical soft iron core inside the coil of a galvanometer ? (ii) Increasing the current sensitivity of a galvanometer may not necessarily increase its voltage sensitivity. Explain, giving reason. 55/1 15 P.T.O.

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