Written as per the revised syllabus prescribed by the Maharashtra State Board of Secondary and Higher Secondary Education, Pune.

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1 Wtten as pe the evsed syllabus pescbed by the Mahaashta State Boad of Seconday and Hghe Seconday Educaton, une. ecse hyscs II STD. XII Sc. Salent Featues Concse coveage of syllabus n Queston Answe Fomat. Coves answes to all Textual Questons and Intext Questons. Includes Solved and ace Numecals. Includes makng scheme fo Boad Questons fom 203 to 207. Execse, Multple Choce Questons and Topc test at the end of each chapte fo effeve pepaaton. nted at: epo Knowledgecast Ltd., Mumba Taget ublcatons vt. Ltd. No pat of ths book may be epoduced o tansmtted n any fom o by any means, C.D. OM/Audo Vdeo Cassettes o eleonc, mechancal ncludng photocopyng; ecodng o by any nfomaton stoage and eteval system wthout pemsson n wtng fom the ublshe..o. No _2322_JU

2 Contents S. No. Chapte Maks age No. 0 Wave Theoy of lght 03 Intefeence and Dffaon Eleostatcs Cuent Electy Magnetc Effe of Elec Cuent Magnetsm Eleomagnetc Induon Eleons and hotons Atoms, Molecules and Nucle Semconduos Communcaton System Boad Queston ape - Mach Boad Queston ape - July Boad Queston ape - Mach Boad Queston ape - July Note: All the Textual questons ae epesented by * mak All the Intext questons ae epesented by # mak

3 0 Wave Theoy of Lght Subtopcs 0.0 Intoduon 0. Wave theoy of lght 0.2 Wavefont and wave nomal 0.3 Huygens pncple 0.4 Constuon of plane and sphecal wavefont 0.5 efleon and efaon of a plane wavefont at a plane suface 0.6 olasaton 0.7 lane polased lght 0.8 Bewste s law 0.9 olaod 0.0 Dopple effe n lght 0.0 Intoduon Newton s copuscula theoy Maxwell s eleomagnetc theoy lanck s quantum theoy Huygens wave theoy of lght Table 0.0 : ostulates. Evey souce of lght emts lage numbe of tny patcles known as copuscles n a medum suoundng the souce. These copuscles ae pefely elastc, gd and weghtless. The copuscles tavel n a staght lne wth vey hgh speeds whch ae dffeent n dffeent meda. v. One gets a sensaton of lght when the copuscles fall on the etna. v. Dffeent colous of lght ae due to dffeent szes of copuscles.. Maxwell postulated the exstence of eleomagnetc waves. Accodng to Maxwell, lght waves ae eleomagnetc waves whch eque no mateal medum fo the popagaton. So lght can tavel though a medum whee thee s no atmosphee.e., n vacuum. Thus, Maxwell establshed elatonshp between electy and magnetsm.. Max planck poposed quantum theoy n ode to explan black body adaton. Accodng to lanck s quantum theoy, lght s popagated n the fom of packets of lght enegy called quanta. Each quantum of lght (photon) has enegy, E = h whee, h = lanck s constant = Js, = fequency of lght.. Lght enegy fom a souce s popagated n the fom of waves: The patcles of the medum vbate about the mean postons n the fom of smple hamonc moton. Thus, the patcles tansfe enegy fom one patcle to ts neghboung patcle and each the obseve. In homogeneous sotopc medum, the velocty of wave emans constant: Speed of the wave s not affeed because densty and tempeatue of sotopc medum ae same thoughout. Dffeent colous of lght waves ae due to dffeent wavelengths of lght waves: Each wave has ts own wavelength. As the wavelength changes, ts colou and fequency also changes. Ths s ndcated by change n the colou. v. The mateal medum s necessay fo the popagaton of wave: eodc dstubance s ceated n the medum at one place whch s popagated fom that place to anothe place. The medum only caes dstubance and hand t ove to the next patcle. To explan the popagaton of lght waves though vacuum, Huygens suggested the exstence of a hypothetcal medum called lumnfeous ethe.

4 Std. XII Sc.: ecse hyscs - II 0. Wave theoy of lght Q.. State the dawbacks of Newton s copuscula theoy. Dawbacks of Newton s copuscula theoy:. It could not explan patal efleon and efaon at the suface of a tanspaent medum. It was unable to explan phenomenon such as ntefeence, dffaon, polasaton etc. Ths theoy peded that speed of lght n a dense medum s moe than the speed of lght n a ae medum whch was expementally poved wong by Focault. Hence Newton s copuscula theoy was ejeed. v. When patcles ae emtted fom the souce of lght, the mass of the souce of lght must decease but seveal expements showed that thee s no change n the mass of the souce of lght. Q.2. State demets of Huygens wave theoy of lght. Demets of Huygens wave theoy of lght:. Ths theoy could not explan elnea popagaton of lght. It could not explan polasaton of lght, Compton effe, photoelec effe etc. It could not explan popely the popagaton of lght though vacuum. Ths s because ethe has hgh elastc constant and zeo densty whch gves contadoy esults. v. Accodng to Huygens wave theoy, lumnfeous ethe medum exsts eveywhee n the unvese even n vacuum whch s teated as mateal medum fo popagaton of lght waves. Howeve, Mchelson s and Moley s theoy dsappoved the exstence of ethe medum. Q.3. State the mets of Huygens wave theoy of lght. Mets of Huygens wave theoy of lght:. It gves satsfaoy explanaton fo laws of efleon, efaon and double efaon of lght assumng tansvese natue of the lght waves. It also explans the theoy of ntefeence and dffaon. It expementally poved that velocty of lght n ae medum s geate than that n a dense medum. 0.2 Wavefont and wave nomal Table 0. Wavefont Wave nomal Wave suface A pependcula dawn to the suface of a wavefont at any pont of a wavefont n the deon of popagaton of lght waves s called a wave nomal. A Locus of all the ponts of the medum to whch waves each smultaneously so that all the ponts ae n the same phase s called wavefont. The suface of sphee wth souce as cente and dstance tavelled by lght wave as adus whee each wave aves smultaneously s called wave suface. Types of wavefonts Sphecal wavefont lane wavefont Cylndcal wavefont A wavefont ognatng fom a pont A wavefont ognatng fom a pont A wavefont ognatng fom a lnea souce of lght at fnte dstance s souce of lght at nfnte dstance s souce (slt) of lght at a fnte dstance called sphecal wavefont. called plane wavefont. s called cylndcal wavefont. S 2 Q Q Q 2 2 Souce at nfnty ay of lght (Wave nomal) ay of lght (Wave nomal) Example: Candle flame poduces sphecal wavefont. 2 Sphecal wavefont lane wavefont Example: The lght fom the Sun eaches the suface of the Eath n the fom of plane wavefont. Cylndcal wavefont Example: A tube lght emts cylndcal wavefont.

5 Chapte 0: Wave Theoy of Lght 0.3 Huygens pncple *Q.4.State Huygens pncple. It s the geometcal constuon to detemne new poston of a wavefont at any late nstant fom ts poston at any eale nstant. Statement:. Evey pont on the pmay wavefont as as a seconday souce of lght and sends out seconday waves (wavelets) n all possble deons. The new seconday wavelets ae moe effeve n the fowad deon only (.e., deon of popagaton of wavefont). The esultant wavefont at any poston s gven by the tangent to all the seconday wavelets at that nstant. 0.4 Constuon of plane and sphecal wavefont *Q.6. Explan the Huygens constuon of plane wavefont.. A plane wavefont s fomed when pont of obsevaton s vey fa away fom the pmay souce. Let Q epesent a plane wavefont at any nstant. Accodng to Huygens pncple, all the ponts on ths wavefont wll a as seconday souces of lght sendng out seconday wavelets n the fowad deon. Daw hemsphees wth, Q,. as centes and as adus. The suface tangental to all such hemsphees s Q. at nstant t. It s a new wavefont at tme t. v. The plane wavefonts s popagated as plane waves n homogeneous sotopc medum. They ae paallel to each othe. Q.5. Dstngush between pmay souce of lght and seconday souce of lght. No. may souce of lght Seconday souce of lght. It s a eal souce of It s a ftous souce lght. It sends out pmay waves n all possble deons. may wave s effeve at evey pont on ts suface. v. may souce s stuated n a. of lght. It sends out seconday waves only n the fowad deon. Seconday wave s effeve only at the ponts whee t touches the envelope. Seconday souce s stuated on a wavefont. *Q.7. Explan the Huygens constuon of sphecal wavefont.. Sphecal wavefont s fomed when souce of lght s at a fnte dstance fom pont of obsevaton. Let S be the pont souce of lght n a. Q epesents sphecal wavefont at any nstant. The wavefont Q as as a pmay wave whch s popagated though a. Accodng to Huygens pncple, all the ponts on Q wll a as seconday souces of lght and send seconday wavelets wth same velocty c n a. v. To fnd out new wavefont at a late nstant t, daw hemsphees wth, Q,. as centes and as adus n the fowad deon. Q Q N N 2 S Q N Q N 2 N 3 Q: lane wavefont at any nstant, Q : lane wavefont afte tme t, N, QQ N 2, N 3 : wave nomals at Q N 3 Q : may wavefont, Q : Seconday wavefont afte tme t, SN, SQN 2, SN 3 : Wave nomals at, Q, 3

6 Std. XII Sc.: ecse hyscs - II v. N, QQ N 2, N 3 ae the wave nomals at, Q, espevely. These wave nomals show the deon of popagaton of plane wavefont. v. The new wavefont Q s paallel to pmay wavefont Q. v. The suface tangental to all such hemsphees s an envelope at that nstant t. Such a suface s passng though the ponts,q,.on the hemsphees and touchng all the hemsphees. Ths suface s the new wavefont at that nstant t. v. SN, SQN 2, SN 3 ae the wave nomals at, Q, espevely. v These wave nomals show the deon of popagaton of sphecal wavefont. v The new wavefont Q s paallel to Q at evey nstant. Note The ntensty of seconday waves vaes fom maxmum n fowad deon to zeo n backwad deon. Ths ndcates that seconday waves ae effeve only n fowad deon. 0.5 efleon and efaon of a plane wavefont at a plane suface *Q.8. Wth the help of a neat dagam, explan efleon of lght fom a plane efleng suface on the bass of wave theoy of lght. Laws of efleon:. The ncdent ays, efleed ays and nomal to the efleng suface at the pont of ncdence, all le n the same plane. The ncdent ays and the efleed ays le on the opposte sdes of the nomal. The angle of ncdence s equal to angle of efleon..e., =. Explanaton: *Q.9. Explan efaon of lght on the bass of wave theoy. Hence pove laws of efaon. Laws of efaon:. The ncdent ays, efaed ays and nomal le n the same plane. Incdent ay and efaed ay le on opposte sdes of nomal. ato of velocty of lght n ae medum to velocty of lght n dense medum s a constant called efave ndex of dense medum w..t. ae medum. Explanaton: M B T N B M M X A A B efleon of lght XY : lane efleng suface AB : lane wavefont B : efleng wavefont A M, B N : Nomal to the plane AA M = BB N = = Angle of ncdence TA M = QB N = = Angle of efleon Q Y X A A N efaon of lght Y glass ( 2 ) XY : plane efang suface AB : ncdent plane wavefont B : efaed wavefont AA, BB : ncdent ays A, B : efaed ays AA M = BB M = : angle of ncdence A N = B N = : angle of efaon N B a ( ) 4

7 Chapte 0: Wave Theoy of Lght. A plane wavefont AB s advancng oblquely towads plane efleng suface XY. AA and BB ae ncdent ays. When A eaches XY at A, then ay at B eaches pont and t has to cove dstance B to each the efleng suface XY. Let t be the tme equed to cove dstance B. Dung ths tme nteval, seconday wavelets ae emtted fom A and wll spead ove a hemsphee of adus A, n the same medum. Dstance coveed by seconday wavelets to each fom A to n tme t s same as the dstance coveed by pmay waves to each fom to B. Thus A = B =. v. All othe ays between AA and BB wll each XY afte A and befoe B. Hence they wll also emt seconday wavelets of deceasng ad v. The suface touchng all such hemsphees s B whch s efleed wavefont, bounded by efleed ays A and B Q. v. Daw A M XY and B N XY. Thus, angle of ncdence s AA M BB N and angle of efleon s MA NB Q. A B = 90 B A = 90 v In A B and A B A B A B A = B (efleed waves tavel equal dstance n same medum n equal tme). A B = A B (common sde) A B A B A B = B A 90 = 90 = v Also fom the fgue, t s clea that ncdent ay, efleed ay and nomal le n the same plane. x. Ths explans laws of efleon of lght fom plane efleng suface on the bass of Huygens wave theoy.. Let XY be the plane efang suface sepaatng two meda a and glass of efave ndces and 2 espevely. A plane wavefont AB s advancng oblquely towads XY fom a. It s bounded by ays AA and BB whch ae ncdent ays. When A eaches A, then B wll be at. It stll v. has to cove dstance B to each XY. Accodng to Huygens pncple, seconday wavelets wll ognate fom A and wll spead ove a hemsphee n glass. v. All the ays between AA and BB wll each XY and spead ove the hemsphees of nceasng ad n glass. The suface of tangency of all such hemsphees s B. Ths gves se to efaed wavefont B n glass. v. A and B ae efaed ays. v Let c and c 2 be the veloctes of lght n a and glass espevely. v At any nstant of tme t, dstance coveed by ncdent wavefont fom to B = B = c t Dstance coveed by seconday wave fom A to = A = c 2 t. oof of laws of efaon:. Fom fgue, AA M + MA = 90 and MA + A B = 90 Fom equatons () and (2), AA M = A B = Smlaly, NA = N B = We have, N B + N B = 90 and N B + A B = 90 Fom equatons (3) and (4), N B = A B =. (). (2). (3). (4) In A B, sn = B = AB AB.(5) v. In B A AB = 2 AB.(6) v. Dvdng equaton (5) by (6), sn sn = /AB /AB = sn 2 2 sn = c c2.(7) c Also c = μ2 2 μ = 2.(8) whee 2 =.I. of glass w..t a. sn sn = μ2 μ v. Fom the explanaton, t s clea that ncdent ays AA, BB, efaed ays A, B and nomal MN and M N le on the same plane XY. Also ncdent ay AA and efaed ay A le on opposte sdes of nomal MN. Hence, laws of efaon can be explaned. 5