PhysicsAndMathsTutor.com 12

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1 PhysisAndMathsTutor.om M. (a) sin θ = or.33 sin θ =.47 sin44 or sin () θ = 50.5, 50., ( ) () answer seen to > sf (b) refrats towards normal () 44 shown () () (TIR) only when ray travels from higher n to lower n or (water to glass) is lower n to higher n () do not allow density, allow optial density, n or refrative index only (d) sin θ = or.47 sin θ = ( ) sin90 () θ = 4.86 (= 43.0( )) ()

2 PhysisAndMathsTutor.om 3 (e) [9] M. (a) reflets at orret angle by eye (use top of 7 and bottom of 4 as a guide) or 7 or 63 orretly marked () refrats away from normal at glass/air () symmetrial by eye or refrated angle (4 ) orretly marked and at least one normal line added () 3 (b) (n g ) = () DNA 4/7 =.56 =.47 (.474) 3 sf shown () () 63 ( ) () allow 6 to 6.99 with reasoning, allow slightly less than 63 without reason given

3 PhysisAndMathsTutor.om 4 (d) =.474 sin () () or use of n =.5 =.3() or.34 if n =.5 used () [8] M3. (a) (i) ladding (ii) sin θ =.4/.46 θ = 75.0 ( ) (74.96) (b) (i) 65 (degrees) (ii).46 sin 65 =.4 sin r or sin r = ef bi r = 70 (degrees) (69.79) ef bi () Two from: less light is lost better quality signal / less distortion inreased probability of TIR Less hange of angle between eah refletion reflets more times (in a given length of fibre) keeping (inident) angle large(r than ritial angle) (angle of inidene is) less likely to fall below the ritial angle less refration out of the ore improved data transfer / information / data / signal arried quiker less multipath dispersion (smearing / overlap of pulses) [8]

4 PhysisAndMathsTutor.om 5 M4. (a) (i) A: ladding + B: ore () (ii) refration towards the normal line () ontinuous lines + strikes boundary + TIR orret angles by eye + maximum TIRs () (b) or = () 80.6 or 80.8 or 8 ( ) only () () to redue multipath or multimode dispersion () (whih would ause) light travelling at different angles to arrive at different times/pulse broadening/merging of adjaent pulses/ smearing / poor resolution/lower transmission rate/lower bandwidth/less distane between regenerators () or to prevent light/data/signal loss (from ore or fibre) () (whih would ause) signal to get weaker/attenuation/rossover/data to be less seure () (d) orret appliation () (endosope, ytosope, arthrosope et, ommuniations et) linked signifiant benefit stated eg improve medial diagnosis/improve transmission of data/high speed internet () [9]

5 PhysisAndMathsTutor.om 6 M5. (a) (i) (using n sin θ = n sin θ or sin θ = n /n gives) orret substitution in either equation (eg.55 sin =.45 (sin 90) or sin =.45/.55) () = (aept less sf) () = 69.3( ) () (aept 69.4, 69 or 70 ) (ii) (iii) the angle (of inidene) is less than the ritial angle or values quoted () (using n sin θ = n sin θ gives).55 sin 60 =.45 sin θ () (sin θ =.55 sin 60/.45 =) or 0.96 or 0.93 () θ = 67.8 () (aept 68 or 68.4) 7 (b) any two from: keeps signals seure () maintains quality/redues pulse broadening/smearing (owtte) () it keeps (most) light rays in (the ore due to total internal refletion at the ladding-ore boundary) () it prevents srathing of the ore () (keeps ore away from adjaent fibre ores) so helps to prevent rossover of information/signal/data to other fibres () ladding provides (tensile) strength for fibre/prevents breakage () given that the ore needs to be very thin () max [9] M6. (a) derease onstant derease 3

6 PhysisAndMathsTutor.om 7 (b) straight ray (ignore arrow) refleting to the right refleted angle = inident angle (aept orret angle labels if refleted angle is outside tolerane) () (i) (n = ) use of 3 ( 0 8 ) = =.47 (.4706) (must see 3 sf or more) (ii) sin θ = or orret substitution in un-rearranged formula θ = 80.4 (80.40) (80.3 to 80.54) ( 80 ) must see 3 sf or more (d) angle of refration = = 9.6 sinθ = 47(06) sin 9.6 = 0.5 ef from first mark θ = 4 (= 4.94 ) ef from first mark range 3 to 5 due to use of rounded values 3 (e) (redued amplitude) due to absorption/energy loss (within the fibre)/attenuation/sattering (by the medium) /loss from fibre (pulse broadening aused by) multi-path (modal) dispersion /different rays/modes propagating at different angles/non a ial ray take longer time to travel ame di tane along fibre as axial rays [4]

7 PhysisAndMathsTutor.om 8 M7. (a) property (of laser light) explanation monohromati ollimated oherent polarised waves of single frequeny/wavelength produes an approximately parallel beam waves produed are in onstant phase vibrations in plane only two orret properties ()() eah orret explanation ()() (if explanation ontradits property, no mark for explanation) 4 (b) (i) stepped graph: n =.5 A to B () n lower and onstant between.5 and.0 B to C () n onstant at.0: C to D () (ii).5 = () i = 5(.)º () (iii) light does not enter the ladding so annot pass aross from one fibre to a neighbouring fibre () fibres without ladding an allow light to pass between fibres when the surfae of the fibre beomes srathed or moisture links two adjaent fibres optially () personal data (suh as bank aount information) must be transmitted along fibres from whih there is no danger of leakage of light resulting in a breah of seurity () 8 []