ISC 2012 Physics Paper-1 Question Paper

8/2/2019 ISC 2012 Physics Paper-1 Question Paper

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PHYSICSPaper-l(THEORY)

(Three hours)(Candidates are allowed additional 15 minutes for only reading the paper.

They must NOT start writing during this time.)Answer all questions in Part I and six questions from Part II, choosing two questions

- from each-of the Sections A, Band C.All working, including rough work, should be done on the same sheet as, and adjacent to,

the rest of the answer.The intended marks for questions or parts of questions are given in brackets [ ].

(Material to be supplied: Log tables including Trigonometric functions.)A list of useful physical constants is given at the end of this paper.PART I

Answer all questions

Question 1A Choose the correct alternative A, B, Cor D for each of the questions given below:

(i) A body has a positive charge of 8 x l O - 1 9C. Ithas:[5]

(A) an excess of 5 electrons(C) an excess of 8 electrons

(B) a deficiency of 5 electrons(D) a deficiency of 8 electrons

(ii) Figure 1 below shows five de sources (cells). Their emfs are shown in the figure.IV 2V 5Vr-----li I I I 1 11------,

B4V 4VII~--------~II~--~~~~------~I~ I~

A

Emf of the battery AB is:(A) 8V(C) 4V

Figure 1(B) 16V(D) 2V

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(iii) W hich one of the fo llow ing graphs in Figure 2 represents variation of reactance'Xc' of a capacitor w ith frequency ~rof an ac supp ly:(A) (8)

(C) (D) t

Figure 2(iv) W hite ligh t is passed th rough sod ium vapours contained in a th in walled g lass flask

and the transm itted ligh t is exam ined w ith the help of a spectrom eter, The spectrumso obtained is:(A ) Absorption spectrum(8) So lar spectrum(C) Band spectrum(D ) Continuous spectrum

(v) B ind ing energy of a nucleus is o f the order of:(A ) E lectron vo lt (eV ) (8) K ilo elec tron volt (K eV )(C ) M ega electron volt (M eV) (D ) ajoule (J)

B . Answer all questions briefly and to the poin t:(i ) A point charge of 5 x 10-6 C experiences a fo rce of 2)( 10-3 N when kept in a

un iform electric field of in tensity E . F ind E .(ii) W hich conservation princip le is invo lved in K irchoff's first law of electric circuits?(Hi) Write an expression of magnetic flux density '8 ' at a po int in end - on position or

an axial position of a m agnetic dipole. (D erivation no t requ ired.)(iv) In a moving co il galvanometer, what is Incan t by a radial m agnetic field?

[15]

-------------------- . . _ - - - - - - - - _ .. _ - - - - - - - - - .. -------------------_ .. . _ - - - _ .. _ - - . . . . . . . . - - - _ .. . _ - " " . . . . _ - - . . . . . . . . . _ _ . . . . . . . . -- .. . - . . . . - - _ . . . . . . . . ; . - . . . . . . . . - .. . - ... "" . . - _ . . . . . - - _ . . . . . . . . . . .2

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- ~ -.- ..~ ------------------------_ ........... -~~ ........... .. .. _= ---- . .. .

(v) V aria tion of alternating current' I'with tim e 't' is show n in the graph below :

ytI(A) x- s J 2 t (sec on d)W hat is the rms value.of this current?

(vi) W hich electrom agnetic radiation has wavelength greater than that of X rays andsmaller than that o f v isib le lig ht?(vii) H ow did Fresnel construct a biprism in order to study interference of light?(viii) S tate B rewste r's la w o f p ola risatio n of light.(ix) A th in convex lens (Lj) o f fo cal le ng th 80 em and a thin concave lens (L2) o f fo callength f a re k ep t c o-a xia lly , 20 em apart as shown in Figure 3 below . W hen anarrow and paralle l beam of light is incident on the convex lens, beam em ergingfrom the concave lens is also a parallel beam . Find!

TJI L2

(x)


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PART II.Answer six questions in thispart, choosing two questionsfrom each of the Sections A, Band C.

SECTION AAnswer any two questions

Question 2(a) Three point charges QJ = ~5 f. 1 C, Q2 = 50 J - l C and Q3 = 100 f. 1 C, are kept at the [4]

corners A, Band C respectively of an equilateral triangle ABC having each sideequal to 75m. Calculate the total electrostatic potential energy of the system.

(b) Obtain an expression for equivalent capacitance C, when three capacitors having [3]capacitance CJ, C2 and C3 are connected in series.

(c) When a potential difference of 3V is applied between the two ends of a 60 em long [2]metallic wire, current density in it is found to be lx10-7 Am-2. Find conductivity ofthe material of the wire in SI system.

Question 3(a) In the circuit shown in Figure 4 below, E is a battery of emf 6V and [4]

internal resistance 1Q. Find the reading of the ammeter A, if it has negligibleresistance: Rl=3QI---~M

Rs=8Q

Figure 4(b) With the help of a neatly drawn and labelled diagram, obtain balancing condition of [3 Ja Wheatstone bridge.

(c) State any two differences between Peltier effect and Joule effect. [2]

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Question 6(a) You are provided w ith a narrow and parallel beam of light. S tate how you w ill [3]

determ ine experim entally, whether it is a beam of ordinary (unpolarised) light,partially polarised light or com pletely polarised light.

(b) For any prism , show that refractive index of its m aterial is given by: [3]_ S in ( A +2o m )

nO,r u= . ( ' A )Sin -2w here the term s have their usual m eaning.

(c ) Figure 6 below shows a parallel beam of monochromatic light incident on a convex [2]spherical surface, radius of curvature R = 30 cm , which separates glass(refractiv e in dex = 16) from air. F ind the position of the im age formed due torefraction of ligh t at this single spherical surface.

Figure 6Question 7

(a) (i) W hat is m eant by:(A) Sphe ric al a be rr atio n?(8) Ch romatic a be rr atio n?

(ii) How can spherical aberration be reduced/m inim ized? Suggest anyone method.(b) A compound m icroscope consists of an objective of focal length 2 em and an [3]

eye piece of focal length 5 cm . W hen an object is kept 24 ern from the objective,final im age formed is virtual and 25 em from the eye piece. Determ ine magnifyingpower of th is com pound m icroscope in this set up i.e. in norm al use.

[3]

(c) (i) Define R eso lv in g P ower of a sim ple astronom ical telescope.(ii) S tate one advantage of a reflecting telescope over refracting telescope.

[2]

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S .E CT IO N CA n sw er an y two questions

Question 8(a) E lectrons hav ing a velocity v of 2x 106ms-l pass undev iated through a uniform [2]

e lec tr ic f ie ld E o f i nte n si ty 5x 101Ym-! and a uniform m agnetic fieldB .(i) Find the m agnitude of m agnetic flux density B of the m agnetic field.(ii) What is the direction of B , if v is tow ards right and E is v ertic ally

dow nw ards in the p lane of this paper?(b) M onochrom atic light of w aveleng th 198 1 1 m is incident on the surface of a m etal, [3]

w hose w ork function is 25 eV . C alculate the stopping potential.(c) Energy levels of Hatom are given by:

En=-1 3~ 6 eV,n-[3 ]

where n is Principal Q uantum num ber. C alcu late the w avelength of electrom agneticrad iatio n em itted b y hy drog en atom resulting from th e tran sition : n = 2 to n = 1.

Question 9(a ) (i) W hat is Compton effect? [3J

(li) In C oolidge X -Ray tube (M odern X -Ray tube) how will you vary :(1) in te ns ity o f emitte d X -R ay s?(2) pen etratin g pow er of em itted X -R ays?

(b) Complete the fo llow ing table for a rad ioactive elem ent whose half life is 5 m inutes. [3JA ssum e that you have 32 g of this e lement at start, i.e. at t = 0 .--,._--- I Iutes 0 5 1 0 ] 5 20 25 IIiioactlve 32 lramsT ime 't' in m inAmount of !' cI e leme nt ~ e ft inNow , using this data, plot th e " de ca y c urv e" .

(c) C alculate the energy released w hen an electron annihilates a positron. [2]--- . . . . . _ - - - - - - - _ . . . . . _ . . . . . . . . . _ _ .. . _ _ .. _ - - ' ........ _ .. _ - - - _ . ._ - - - - - - _ .. . _ .. - - - - - - - - - - - - - - - _ . _ - - - - - - - _ . _ - - - - - _ . _ - - - - .. ------------- . .. - - - ~ - - - - - - -- - - - - - -- - - - - -

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Question 10(a) Draw a labelled energy band diagram for a solid which is an insulator. [3]What is the main difference between this diagram and that of a semi-conductor?(b) Figure 7 below shows the circuit of an electronic device:p~ ~M [3]

b

B '----_____i I-----......L.----------lo NFigure 7

(i) Which electronic device: a rectifier, an amplifier or an oscillator does theabove circuit represent?

(ii) State where the input voltage is applied and where the output voltage isavailable.

(iii) Compare the output voltage of this circuit with its input voltage.(c) Prepare a truth table for the combination of gates shown in Figure 8 below: [2]

Figure 8Useful Constants and Relations:

1 . Speed of Light in vacuum (c) = 3.0 X 108 m s"2. Planck's Constant (h) = 6.6 x 10-34 Js3 . Charge of an electron . (-e) = -1.6xlO-19C4. Constant for Columb's law ( 4 ; e J = 9 xl09mFl5 . Mass of an electron (me) = 9 X 10-31 kg6 . 1 electron volt (leV) = 1 .6xlO-19J7 . (lnm) = 1O-9m

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ISC 2012 Physics Paper-1 Question Paper