(a) apparatus: cell with particles e.g. smoke (container must be closed) diagram showing suitable arrangement with light illumination and microscope

Transcription

1 4 Specimen 03 (a) apparatus: cell with particles e.g. smoke (container must be closed) diagram showing suitable arrangement with light illumination and microscope (b) specks / flashes of light in random motion (c) cannot see what is causing smoke to move hence molecules smaller than smoke particles () continuous motion of smoke particles implies continuous motion of molecules () random motion of particles implies random motion of molecules () max. 37 (a) equatial bit / above equat satellite moves from west to east / same direction as Earth spins period is 4 hours / same period as spinning of Earth (allow mark f appears to be stationary/overhead if none of above marks sced) (b) gravitational fce provides/is the centripetal fce GMm/R = mrω GMm/R = mv/r ω = π /T v = πr / T clear substitution clear wking to give R3 = (GMT / 4π) (c) R3 = (4 3600) / 4π = R = m (missing out 3600 gives.8 05 m and sces /3 marks) (a) (b) (c) electrons fired at metal target... electrons decelerated giving off (e.m.) radiation... range of decelerations, so continuous spectrum... also, electrons in inner bits are excited... de-excitation gives characteristic line spectrum... (i) increase cathode/tube current... (ii) increase anode voltage... (iii) use aluminium filter (allow metal filter)... I = I0e-µx In = 0.40µ µ =.733 cm- = In/ = e-.733x x =.33 cm...

2 4 Specimen 03 (a) high frequency wave the amplitude the frequency is varied the variation represents the infmation signal / in synchrony with (the displacement of) the infmation signal. B3 (a) (i) amplitude (modulated) (allow AM )... (ii) carrier (frequency / wave)... (iii) sideband (frequency)... (b) 0 khz... (c) sketch: general shape i.e. any wave that is amplitude modulated... crect period f modulating wavefm (00 µs)... crect period f carrier wavefm (0 µs)... (a) e.g. noise can be eliminated/wavefm can be regenerated extra bits of data can be added to check f errs cheaper/me reliable greater rate of transfer of data ( each, max ) B (b) receives bits all at one time transmits the bits one after another (c) sampling frequency must be higher than/(at least) twice frequency to be sampled either higher (range of) frequencies reproduced on the disc lower (range of) frequencies on phone either higher quality (of sound) on disc high quality (of sound) not required f phone (b) e.g. shter aerial required longer transmission range / lower transmitter power / less attenuation allows me than one station in a region less disttion (allow any three sensible suggestions, mark each) 50 63

3 70 (a) pulse (of ultrasound) produced by quartz / piezo-electric crystal reflected from boundaries (between media) reflected pulse detected by the ultrasound transmitter signal processed and displayed intensity of reflected pulse gives infmation about the boundary time delay gives infmation about depth (four B marks plus any two from the four, max. 6) Specimen 03 B [6] (b) shter wavelength smaller structures resolved / detected (not me sharpness) (c) (i) I = I0 e µx ratio = exp( ) ratio = 0.3 (ii) later signal has passed through greater thickness of medium so has greater attenuation / greater absption / smaller intensity 87 (a) (b) 9 large/unifm magnetic field applied (to patient) pulse of radio-frequency waves Causes H-atoms in patient to resonate vibrate at Lamour frequency H-atoms give off radio-frequency waves RF detected and processed to give positions of H-atoms non-unifm magnetic field enables positions of resonating atoms to be defined [ each, any five] e.g. cost, ptability of equipment, time taken [any sensible suggestions, each, max ] (a) (i) metal (allow specific example of a metal) (ii) e.g. provides return f the signal shields inner ce from interference/reduces cross-talk/reduces noise increased security (any two sensible suggestions, each) (b) (i) (gradual) loss of power/intensity/amplitude (ii) db is a log scale either large (range of) numbers are easier to handle (on a log scale) compounding attenuations/amplifications is easier (c) attenuation = =.09 db B.09 = 0 lg(pout / PIN) ratio = 0.6 B5 B B B C

4 0 Specimen 03 (a) (i) loss of (signal) power (b) f digital, only the high and the low / and 0 are necessary variation between highs and lows caused by noise not required (c) attenuation = 0 lg(p / P) either 95 = 0 lg({.4 03} / P) 95 = 0 lg(p /.4 03) P = W (ii) unwanted power (on signal) that is random (a) signal becomes distted / noisy signal loses power / energy / intensity / is attenuated (b) (i) either numbers involved are smaller / me manageable / cover wider range calculations involve addition & subtraction rather than multiplication and division (ii) 5 = 0 lg(pmin / (6. 0 9)) minimum signal power = W signal loss = 0 lg( )/( ) = 35 db maximum cable length = 35 /.6 = 85 km so no repeaters necessary 7 3 (a) (i) use of En = 3.6 ev / n use of E = hf n=3 (ii) E5 E = 3.6 / / 5 =.856 ev convert.856 ev to J f = / = 689 ( 0 Hz) (b) f = 4 0 (Hz) v = / 67 = (m s ) [8]

5 Specimen 04 (a) obeys the equation pv = constant T pv = nrt p, V and T explained at all values of p, V and T/fixed mass/n is constant (b) (i) = n n = 0.34 mol A0 (a) acceleration / resting fce is proptional to displacement / centre of displacement / oscillation acceleration / resting fce is in the opposite direction to displacement (b) suitable example e.g. (simple) pendulum, mass-spring oscillat (c) velocity drawn as a cosine wave acceleration drawn as a minus sine wave amplitude of graphs constant (d) (i) ω = πf = π 879 = 550 rad s (ii) f total mass/amount of gas (.5 +.6) = ( ) 8.3 T T = 360 K (c) when tap opened gas passed (from cylinder B) to cylinder A wk done on gas in cylinder A (and no heating) so internal energy and hence temperature increase (ii) use of E = 3 4 significant figures only maω = = 0.89 (J) (a) series of X-ray images (f one section/slice) taken from different angles to give image of the section/slice repeated f many slices to build up three-dimensional image (of whole object) (b) deduction of background from readings division by three (iii) 6% of energy of one cycle = = 0.03 (J) power output = = 9.95 (W) 3 P = 5 Q = 9 R = 7 S =3 (four crect /, three crect /) A

6 4 (a) amplitude modulation (allow AM)... (b) (i) frequency = / period... = 00 khz... (ii) frequency = 0 khz... (c) (i) vertical line at 00 khz... vertical lines at 90 khz and 0 khz... lines at 90 khz and 0 khz same length and shter than at 00 khz... (ii) 0 khz 5 Specimen (a) frequency of carrier wave varies (in synchrony) with signal (in synchrony) with displacement of signal (b) advantages e.g. B4 less noise / less interference greater bandwidth / better quality ( each, max ) disadvantages e.g. sht range / me transmitters / line of sight me complex circuitry greater expense ( each, max ) 86 (a) (b) (i) (ii) 70 8 piezo-electric/quartz crystal across which is applied an alternating voltage crystal vibrates at its resonant frequency trace length = 4.0 mm distance = speed x time = 450 x 0.4 x 0 x 0-6 = 5.8 x 0-3 m thickness = 0.9 cm trace length = 5. cm thickness = 4. cm (a) crect values of, 5, 0, 5 and 4 ( each err) graph drawn as a series of steps steps occurring at crect times B (b) sample me frequently greater number of bits (a) strong unifm (magnetic) field either aligns nuclei gives rise to Larm/resonant frequency in r.f. region non-unifm (magnetic) field either enables nuclei to be located changes the Larm/resonant frequency (b) (i) difference in flux density = = T (ii) f = c B = =.6 04 Hz

7 93 (a) multiple reflections with i = r... (b) all rays to have same path length/prevent (multipath) dispersion OR easier to ste/handle... e.g. greater bandwidth no cross-talk reduced noise smaller size and weight cheaper security suited to digital transmission.. ( each, max 3)... A3 (c) 0 0 (a) e.g. large bandwidth/carries me infmation low attenuation of signal low cost smaller diameter, easier handling, easier stage, less weight high security/no crosstalk low noise/no EM interference (allow any four sensible suggestions, each, max 4) B4 (b) (i) infra-red (ii) lower attenuation than f visible light (c) (i) gain/db = 0 lg(p/p) 6 = 0 lg(p/ ) P = W (ii) power loss along fibre = = 6.0 db either 6 = 0 lg(p/ ) 6 db = = 0 lg(p/ ) input power =.5 0 W Specimen 04 (a) loss / reduction in power / energy / voltage/ amplitude (of the signal) (b) (i) attenuation = 5 7 = 875 db B (ii) 0 amplifiers gain = 0 43 = 860 db (c) gain = 0 lg(p/p) overall gain = 5 db / attenuation is 5 db 5 = 0 lg(p / 450) P = 4 mw W 4 (a) (i) thermal energy (in the cable) / resistance (ii) loss = 0 lg(0.55 / 0.60) = (-) 0.38 db loss per unit length = 0.38 / = 5.0 db km (b) (i) unwanted (random) signal power (ii) e.g. molecular/lattice vibrations, pick-up of e.m. signals any two sensible suggestions, each, max B

8 7 3 Specimen 04 (a) any five from use of a suitable named metal lamp must be UV unless sodium similar is used detect of emitted electrons electron detect suitable f very low currents description of use electrons emitted (b) (i) same shape graph coming down to zero I at the same point parallel on the right but lower (ii) maximum kinetic energy is not dependent on intensity number of electrons emitted is directly proptional to intensity (c) (i) (J) (ii) hc / λ / (J) (electron energy =) photon energy wk function (J) 6 4 (a) (i) probability of decay of a nucleus is always constant it is not possible to predict when any given nucleus will decay (ii) rate of decay N OR dn / dt is (only) proptional to N (iii) use of N = N0 e λt when N = e λt = taking logs gives λt = ln (b) (i) N0, t = t½ and t = ln /λ (= / λ) n+ 7 N 6 C+ p left-hand side crect right-hand side crect (ii) λ = ln / 5730 =. 0 4 k k. 0 4 t = e ln =. 0 4 t.5 t = 90 year (iii) large uncertainty because.3 0 is uncertain (7% at best) []