Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level. Published

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1 Cambridge International Examinations Cambridge International Advanced Subsidiary and Advanced Level PHYSICS 9702/42 Paper 4 A Level Structured Questions MARK SCHEME Maximum Mark: 100 Published This mark scheme is published as an aid to teachers and candidates, to indicate the requirements of the examination. It shows the basis on which Examiners were instructed to award marks. It does not indicate the details of the discussions that took place at an Examiners meeting befe marking began, which would have considered the acceptability of alternative answers. Mark schemes should be read in conjunction with the question paper and the Principal Examiner Rept f Teachers. Cambridge will not enter into discussions about these mark schemes. Cambridge is publishing the mark schemes f the series f most Cambridge IGCSE, Cambridge International A and AS Level and Cambridge Pre-U components, and some Cambridge O Level components. IGCSE is a registered trademark. This document consists of 13 printed pages. UCLES 2017 [Turn over

2 1(a) fce per unit mass 1(b)(i) g = GM / r 2 = ( ) / ( ) 2 = N kg 1 1(b)(ii) mass = (960 / 9.81) kg weight on comet = (960 / 9.81) = N 1(c) similarity: e.g. both attractive/pointed towards the comet e.g. same der of magnitude difference: e.g. radial/non-radial e.g. same (over surface)/varies (over surface) UCLES 2017 Page 2 of 13

3 2(a)(i) mean/average square speed/velocity 2(a)(ii) pv = NkT pv = nrt ρ = Nm / V ρ = nn A m / V and k = nr / N E K = ½ m c 2 with algebra to (3 / 2)kT 2(b)(i) no (external) wk done U = q w = 0 q = N A (3 / 2)k 1.0 N A k = R so q = (3 / 2)R M1 2(b)(ii) specific heat capacity = {(3 / 2) R} / = 450 J kg 1 K 1 UCLES 2017 Page 3 of 13

4 3(a)(i) e.g. period = 6 / 2.5 frequency = 0.42 Hz 3(a)(ii) energy = ½ m 4π 2 f 2 2 y 0 = ½ π ( ) 2 = J 3(b)(i) (induced) e.m.f. proptional to rate of M1 change of magnetic flux (linkage) cutting of magnetic flux 3(b)(ii) coil cuts flux/field (of moving magnet) inducing e.m.f. in coil (induced) current in resist causes heating (effect) thermal energy/heat derived from energy of oscillations (of magnet) M1 UCLES 2017 Page 4 of 13

5 4(a) pulse (of ultrasound) * produced by quartz crystal/piezo-electric crystal * gel/coupling medium (on skin) used to reduce reflection at skin reflected from boundaries (between media) reflected pulse/wave detected by (ultrasound) transmitter reflected wave processed and displayed * intensity of reflected pulse/wave gives infmation about boundary * time delay gives infmation about depth of boundary max. 2 of additional detail points marked * B2 4(b) I T = I 0 exp ( µx) 2.9 = exp (4.6µ) µ = 0.23 cm 1 UCLES 2017 Page 5 of 13

6 5(a) any two reasonable suggestions e.g. signal can be regenerated/noise removed (not no noise ) circuits me reliable circuits cheaper to produce multiplexing (is possible) err crection/checking easier encryption/better security B2 5(b)(i) samples the analogue signal M1 at regular intervals and converts it (to a digital number) 5(b)(ii) 1. smaller step depth 2. smaller step height UCLES 2017 Page 6 of 13

7 6(a) fce proptional to product of charges and inversely proptional to the square of the separation M1 6(b)(i) reference to point charges (near to each sphere,) fields are in opposite directions point (between spheres) where fields are equal and opposite point (between spheres) where field strength is zero so same (sign of charge) M1 6(b)(ii) (at x = 5.0 cm,) E = V m 1 and a = qe / m E = ( ) / ( ) = m s 2 6(c) field strength E is potential gradient field strength is rate of change of (electric) potential (field strength) maximum at x = 6 cm M1 UCLES 2017 Page 7 of 13

8 7(a) equal and opposite charges on the plates so no resultant charge +ve and ve charges separated so energy sted 7(b) charge / potential difference M1 reference to charge on one plate and p.d. between plates 7(c) energy = ½ CV 2 energy = ½ QV and C = Q / V (1 / 16) ½ CV 0 2 = ½ CV 2 V = ¼ V 0 UCLES 2017 Page 8 of 13

9 8(a)(i) circle around both diodes 8(a)(ii) indicates (whether) temperature M1 8(b)(i) 8(b)(ii) (is) above below a set value (when resistance of C > R V,) V > V + V + < 3 V p.d. across R V < p.d. across R/Y/3 V p.d. across C > p.d. across R/ X/3 V op-amp output is negative (only) green resistance of C becomes less than R V V < V + green (LED) goes out blue (LED) comes on M1 M1 8(c) changes/determines temperature at which LEDs switch UCLES 2017 Page 9 of 13

10 9(a)(i) Hall voltage depends on thickness of slice thinner slice, larger Hall voltage 9(a)(ii) Hall voltage depends on current in slice 9(b) sinusoidal wave, one cycle at θ = 0 and at θ = 360, V H = V MAX at θ = 180, V H = V MAX UCLES 2017 Page 10 of 13

11 10(a) 10(b)(i) two from: frequency below which electrons not ejected maximum energy of electron depends on frequency maximum energy of electrons does not depend on intensity instantaneous emission of electrons (λ 0 is the) threshold wavelength wavelength cresponding to threshold frequency maximum wavelength f emission of electrons B2 10(b)(ii)1. intercept = 1 / λ 0 = m 1 λ 0 = m 450 nm 10(b)(ii)2. gradient = hc gradient = crect substitution into gradient fmula h = ( ) / ( ) = J s 10(c) line: same gradient straight line, positive gradient, intercept at greater than when candidate s line extrapolated UCLES 2017 Page 11 of 13

12 11(a) loss of (electric) potential energy = gain in kinetic energy qv = ½ mv 2 E K = p 2 / 2m = qv p = mv with algebra leading to p = (2mqV) 11(b)(i) particle/electron has a wavelength (associated with it) dependent on its momentum when/because particle is moving 11(b)(ii) p = ( ) 1/2 λ = ( ) / ( ) = m 11(c) wavelength is similar to separation of atoms M1 so diffraction observed UCLES 2017 Page 12 of 13

13 12(a) 7 0 1e 12(b)(i) E = mc 2 = ( ) 2 M1 = J division by clear to give 934 MeV 12(b)(ii) m = ( u) + ( u) u = ( ) (u) energy = energy per nucleon = ( ) / 139 = 7.85 MeV 12(c) above A = 56, binding energy per nucleon decreases as A increases U-235 has larger nucleon number M1 so less (binding energy per nucleon) fission takes place with uranium fission reaction releases energy binding energy per nucleon less (f uranium than f products) () (M1) () UCLES 2017 Page 13 of 13

Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level. Published

Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level PHYSICS 9702/43 Paper 4 A Level Structured Questions MARK SCHEME Maximum Mark: 100 Published