M.M.A HIGHER SECONDARY SCHOOL - PAPPANADU 12 TH PHYSICS - HALF YEARLY EXAM ANSWER KEY

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1 M.M.A HIGHER SEONDARY SHOOL - PAPPANADU TH PHYSIS - HALF YEARLY EXAM ANSWER KEY STD : XII - EM PART - I Sl. No. Answe Sl. No.. (a) N - m - 6. (c) sommefeld. (c) 4 m 7. (a) (a) Hz Answe 3. (a) zeo volt and zeo V/m 8. (b) (b) continuous spectum 4. (c) 0 9. (a) : 5 5. (c) n : 0. (d) chage 6. (d) 0 o. (a) h(υ - υ 0 ) 7. (a) :. (d) 8 O 6, (b) capacito 3. (d) neuton numbe deceases by one 9. (a) 0 4. (b) (a) zeo 5. (b) 00 MeV. (d) bushes 6. (a) collition. (c) diffaction patten becomes naowe and cowded togethe 7. (a) an amplifie with feedback 3. (c) patially polaized 8. (a) A + B + + D 4. (b) an odd multiple of π 9. (a) the amplitude of caie wave vaies in accodance with the amplitude of the modulating signal 5. (c) 6000 Ǻ and 5980 Ǻ 30. (a) to avoid flicke in the pictue

2 Pat II 3. Applications of capacitos: (i) used in the ignition system of automobile engines to eliminate spaking. (ii) used to educe voltage fluctuations in powe supplies and to incease the efficiency of powe tansmission. (iii) used to geneate electomagnetic oscillations and in tuning the adio cicuits. 3. V q V 4 x 0 4 V State Kichoff s voltage law Kichoff s voltage law states that, the algebaic sum of the poducts of esistance and cuent in each pat of any closed cicuit is equal to the algebaic sum of the emf s in that closed cicuit 34. Distinguish between electic powe and electic enegy. Electic powe is defined as the ate of doing electic wok. Its unit is watt. Electic enegy is defined as the capacity to do wok. Its unit is joule. 35. V R I R480 Ω 36. State Joule s law. H I Rt (i) diectly popotional to the squae of the cuent fo a given R (ii) diectly popotional to esistance R fo a given I (iii) diectly popotional to the time of passage of cuent 37. Define ms value of altenating cuent. The ms value of altenating cuent is defined as that value of the steady cuent, which when passed though a esisto fo a given time, will geneate the same amount of heat as geneated by an altenating cuent when passed though the same esisto fo the same time. 38. e e M di / dt ( I I) / dt (8 4) / m H 39. Define Rayleigh scatteing law. The amount of scatteing is invesely popotional to the fouth powe of the wave length. 40. Define optic axis of a cystal. Inside the cystal thee is a paticula diection in which both the odinay and exta odinay ays tavel with same velocity. This diection is called optic axis of the cystal.

3 4. E v B V.7 x 0 7 m s - 4. Give the pinciple of Millikan s oil dop expeiment. It is based on the study of the motion of unchaged oil dop unde fee fall due to gavity and chaged oil dop in a unifom electic field.by adjusting unifom electic field suitably, a chaged oil dop can be made to move up o down o even kept balanced in the field of view fo sufficiently long time and a seies of obsevations can be made. 43. Define stopping potential. The minimum negative potential given to the anode fo which the photo electic cuent becomes zeo is called the stopping potential 44. What ae the uses of nuclea eactos?. ae mostly aimed at powe poduction.. ae useful to poduce adio isotopes. 3. act as a souce of neutons, hence used in the scientific eseach. 45. Wite shot note on Leptons? Leptons ae lighte paticles having mass equal to o less than about 07 times the mass of an electon except neutino and antineutino. This goup contains paticles such as electon, positon, neutino, antineutino, positive and negative muons. 46. A A f A 00 ( ) A f Wite any thee uses of RO. (i) It is used to measue a.c and d.c voltage. (ii) It is used to study the wavefoms of a.c voltages. (iii) It is used to find the fequency of a.c voltage. 48. V E ---- ½ Maks ---- ½ Maks I c (ma) I B I c I B (µa) 49. What ae univesal gates? Why ae they called so? NAND and NOR gates ae called univesal gates because they can pefom all the thee basic logic functions. Basic logic gates NOT, OR, and AND using NAND and NOR gates. 50. What is meant by skip distance? In the sky wave popagation, fo a fixed fequency, the shotest distance between the point of tansmission and the point of eception along the suface is known as the skip distance.

4 5. Wok done is stoed as electostatic potential enegy Pat III dw V dq q dq U q 5. Diagam VIR q dq (o) V VE-I (o) I E- V I IR E V V E V R V 53. R s R +R +R Ω V 0 I A R 0 V I R x 5 5 V V I R x 3 3 V V 3 I R 3 x V 54. Diagam By connecting low esistance in paallel with it lage potion of the cuent passes though the low esistance S R a G. I I I g g GS G S Ammete does not appeciably change the esistance and cuent in the cicuit ideal ammete has zeo esistance 55. Faaday s laws of electomagnetic induction. Fist law : Wheneve the amount of magnetic flux linked with a closed cicuit changes an emf is induced in the cicuit. The induced emf lasts so long as the change in magnetic flux continues. Second law : The magnitude of emf induced in a closed cicuit is diectly popotional to the ate of change of magnetic flux linked with the cicuit. Lenz s law in electomagnetic induction. Lenz s law states that the induced cuent poduced in a cicuit always flows in such a diection that it opposes the change o cause that poduces it ½ Maks ---- ½ Maks Maks

5 56. D D β (o) d d (calculation) mak 0-3 m (o) mm 57. Any five popeties of X ays mak 58. Explain by Quantum theoy (i) Wok function (ii) Enegy of the incident photon wok function + kinetic enegy of the electon h υ W + mv If the electon does not lose enegy by intenal collisions, hυ W + mv max hυ 0 W h (υ υ 0 ) mv max 59. Diagam v ll 0 c l l 0 v contacted by a facto c example -----½mak 60. Mass of the eactants amu Mass of the poducts amu amu amu 93 MeV Enegy eleased x MeV (OR) Enegy pe fission 00 MeV 00 x 0 6 x.6 x 0-9 J 3 X 0 - J Enegy pe fission x N Total enegy eleased pe second 6 30 The equied numbe of fissions pe second N 30 N X 0 8 fission pe second mak

6 6. Gaph Gain decease at vey low and vey high fequencies Lowe cut off fequency (f L) is defined as the fequency in the low fequency ange at which the gain of the amplifie is / times the mid fequency gain (A M ). Uppe cut off fequency (f U ) is defined as the fequency in the high fequency ange at which the gain of the amplifie is / times the mid fequency gain (A M ). Band width defined as the fequency inteval between lowe cut off and uppe cut off fequencies. BW f U - f L 6. Advantages of digital communication i) The tansmission quality is high and almost independent of the distance between the teminals. ii) The capacity of the tansmission system can be inceased. iii) The newe types of tansmission media such as Light beams in optical fibes and wave guides opeating in the micowave fequency extensively use digital communication. Disadvantages of digital communication (i)a digital system equies lage bandwidth. (ii) It is vey difficult to gadually change ove fom analog to digital tansmission. Pat IV 63. Electic field due to an electic dipole at a point on its equatoial line : Diagam E 4 0 q d along BP E 4 0 q d along PA The vetical components E Sinθ and E Sinθ ae equal and opposite, theefoe they cancel each othe E E cos θ ( E E ) Up to E 4 0 P d 3/ mak p E 3 40 The diection of E is along PR, paallel to the axis of the dipole and diected opposite to the diection of dipole moment

7 64. Diagam Explanation F q ( v B) F B q v mv Bqv mv Bq T Bq m m T Bq and T not depends v and 65. Explanation Pinciple - Electo magnetic induction Es E P N N s p Fo an ideal tansfome, input powe output powe E p I p E s I s, Es N s I up to P k E N I P p Fo step up tansfome k > and Fo step down tansfome k < Efficiency of tansfome. S mak -----mak mak 66. Diagam Explanation sini ( B / A) sin ( AD / A) B AD mt t (i) AD < A - Explanation (ii) AD A - Explanation itical angle definition a m a (iii) AD > A - Explanation Total intenal eflection definition

8 67. Diagam Pinciple Expeimental aangement E Detemination v, v B Ee l y m v e l B Y K m E e ye Up to m K l B e kg m 68. Radioactive law of disintegation : The ate of disintegation at any instant is diectly popotional to the numbe of atoms of the element pesent at that instant (o) log e N - t + t 0, N N 0 log e N 0 N N 0 e - t Gaph dn N dt An infinite time is equied fo the complete disintegation of all the atoms. Half life peiod : Half life peiod statement mak at, t T ½, N N 0 log e T ½ up to T / 69. Diagam Explanation i + i i f v v v R R R out R f R v out v R R R R R f R f v V out - ( V + V ) 70. Diagam AF section RF section f mak mak mak mak mak -----

9 P.MURUGESEN M.Sc., B.Ed., M.Phil., PG TEAHER IN PHYSIS MMA HIGHER SEONDARY SHOOL PAPPANADU THANJAVUR PHONE :

15 B1 1. Figure 1. At what speed would the car have to travel for resonant oscillations to occur? Comment on your answer.

15 B1 1. Figure 1. At what speed would the car have to travel for resonant oscillations to occur? Comment on your answer. Kiangsu-Chekiang College (Shatin) F:EasteHolidaysAssignmentAns.doc Easte Holidays Assignment Answe Fom 6B Subject: Physics. (a) State the conditions fo a body to undego simple hamonic motion. ( mak) (a)