AQA A Level Physics Paper 1 UNOFFICIAL MARK SCHEME (20th May 2019) Watch

bruffsupporter
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Post your answers below and I'll update!
1. NUCLEAR PHYSICS [7]

(State difference between nucleons of 131-I and 125-I) 131 has 6 more neutrons [1]
(What is nucleon number after Beta-minus decay?) 131 [1]
(State two differences between nuclei after electron capture) One less proton, one more neutron [2]
(State 3 differences between internal conversion and Beta-minus decay) Beta-minus changes neutron to proton (change in nucleus structure), Beta-minus emits antineutrino, Beta-minus involves weak interaction, Electron emitted in Beta-minus is created in the decay [3]


2. OPTICS [12]

(Suggest how LED-Prism design ensures ray doesn't deviate) Light incident along normal [1]
(Suggest 2 ways that Prism-windscreen design ensures ray doesn't deviate) RI of prism and glass same, no gap between prism and windscreen gap to ensure no refraction/deviation in air [2]
(Explain path of light inside windscreen) Critical angle = 41.1°, incident angle greater than critical at A, B and C, TIR occurs [3]
(Explain how variance of RI across thickness of glass affects ray's path)
This is essentially equivalent to passing through many boundaries with a small Ri difference, causing the light to travel in a curved path. May cause light to pass out of windscreen due to changed angle of incidence. [2]
(Explain why water droplets reduce light intensity) Increased critical angle, no TIR occurs, some light refracts into water, only partial reflection. [2]
(Discuss how extending length would change detector signal) - More of the light is absorbed so the signal is weaker, harder to detect changes in signal strength, less sensitive
Reflects off the glass more times, so more likely to hit a drop, more sensitive [2]


3. WAVES [8]

(Describe pattern seen on screen) - central maximum, around it are alternating minima and maxima of the same width. Central maximum is double width. Intensity of maxima drops off quickly. Parallel fringes to the slit. Green. [2]
(Describe differences when green light replaced by red light) fringes red, fringes wider and bigger spaces between. [2]
(Find order between 1st order and central maximum) 19° [2]
(In practice, light is of range 600-700nm. Explain differences.) More blurry, lower peak intensity and shallower intensity gradient on each fringe. 600nm light on inside of fringes, 700nm light on outside of fringes. [3]


4. MECHANICS (Moments) [12]

(Explain why tension in rope is unaffected by weight of beam or empty box)
The pivot is positioned such that the moments of the beam and empty box are equal in magnitude, so cancel. Under centre of mass of object [2]
(Find tension in rope) 2600N - take moments about the pivot [5]
(Find range) 22m [2]
(Discuss what would happen to range if mass released before vertical) [3]
It starts with some initial vertical velocity, increasing time if flight, increasing range. (Increased vertical velocity overrides decreased horizontal velocity) (lots of options)


5. MECHANICS [12]

(Show Initial KE = 700kJ) Find horizontal momentum [2]
(Find momentum parallel to barrier) 43000 kgms^-2 [3]
(Show change in KE = 80kJ) Horizontal momentum = mucos(20), so since no change in horizontal momentum, so v = ucos(20), sub in ½ mv^2 - ½mu^2. [2]
(Determine whether steel would be a suitable barrier) W = Fs; s = 1.33m so Yes.
Alternatively using s = 1.5m, W = 60000*1.5 = 90000J > 82kJ from previous part. So Yes. A third alternate approach can involve calculating the acceleration using SUVAT, and then using F=ma to find that remaining force is about 5000-6000N - so yes, the barrier is sufficient.[3]
(Discuss whether steel or concrete would cause less damage to the dummy) Steel, because time taken for momentum to change is shorter for concrete, change in momentum is the same for both materials, force = change in momentum/time, so more force so more damage if concrete used.[2]1


6. SHM/WAVES [5]

(State at which point velocity is maximum positive) 1.5ms (0.5 and 2.5 are incorrect because the velocity there is negative) [1]
(Find max a) 41000 ms^-2 (2sf) [2]
(Describe which type of wave is formed - sound) Longitudinal, oscillations parallel to the direction of propagation of the wave [1]


7. ELECTRICITY [4]

(Explain why V1 decreases when brightness of bulb increases) Mention internal resistance, total R decreases, I increases, V = E - Ir [2]
(Explain why V2 > V1 when identical cell added in parallel) r decreases for 2nd circuit, V = E - Ir [2]


8. MCQ [25]

8. A (Particles in feynman diagram - W+ and electron neutrino)
9. D (Energy given to orbital electron)
10. C (Photoelectric effect - Max KE = 3.3 *10^-19J ?)
11. C
12. C
13. A
14. B
15. D
16. D
17. B
18. C
19. C
20. D
21. B
22. D
23. D
24. C
25. B
26. A
27. C
28. C
29. D
30. D
31. A
32. D (How damping affects amplitude - flattest and broadest graph)


Assorted MCQ:

Van De Graff style moving belt - 0.04Q (B)
Couple does not produce translational motion (C)
Voltmeter and resistor in series with cell, R = 36k ohm (B?) and B here too iirc
Velocity time graph, difference in distances = 40m (A or B?)
Voltage between P and ground = 140V (D)
Units of Power - kgm^2s^-3 (C)
Effect of changing X, L and E on stiffness - 2X, L, 4E (D? Yes did it give 1/8D) yeah i think D too then this one was quite late I think but unfortunately could be either 29 or 30 :^)
Power varying linearly with force/time (B or C)
Quantities the same in both wires - resistivity and current (B)
Oscillations = 99 (C) friccing copyright symbols lmao
Momentum of photon - 4.4x10^-27? (C??)
Particle across plates - alpha particle (D)
Circular motion energy - 2mn^2π^2 (C)
Strain on wire (50N on 1mm^2 area) (calculation: gives 50*10^6) - 10^6-10^9 Pa (C)

Credit to @freebirdk for update. Check out his updated mark scheme (more detailed multi-choice) here: https://docs.google.com/document/d/e...lgwiEC7_b8/pub
Last edited by bruffsupporter; 3 weeks ago
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dansmithson
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shouldn't it have been '6 more neutrons' to be more specific
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The_Governor200
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Hello, for the electric motor and the charge, (multiple choice) it is 0.04Q i believe.
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bruffsupporter
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(Original post by dansmithson)
shouldn't it have been '6 more neutrons' to be more specific
Yep thanks, couldn't remember it off the top of my head
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SenseiChen
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Beta minus emits an antineutrino, not a neutrino
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Fiskjoe123
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1aii) what is the nucleon number after beta decay? = 131
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researchfulpu
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Steel is safer than concrete wall due to momentum impact time etc
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The_Governor200
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For the diffraction grating question, to find d in dsinθ=nλ you do d= l/n where l is 1mm and n is the number of lines per mm. I believe it was 500 or 600 / 1x10^3m (1mm)

One you do that rearrange dsinθ=nλ to sinθ=nλ/d, and then sin-1 the answer?
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GDale133421
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19 degrees?
(Original post by The_Governor200)
For the diffraction grating question, to find d in dsinθ=nλ you do d= l/n where l is 1mm and n is the number of lines per mm. I believe it was 500 or 600 / 1x10^3m (1mm)

One you do that rearrange dsinθ=nλ to sinθ=nλ/d, and then sin-1 the answer?
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The_Governor200
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For the windscreen wiper, the reasons for which the ray won't move was, the led emitter and ray are perpendicular to the first prism?
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The_Governor200
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Yes i got 19 degrees are rounding up from 18. something degrees.
(Original post by GDale133421)
19 degrees?
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dansmithson
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What did people get for the steel barrier test: will it pas/fail Q?
(Original post by bruffsupporter)
Post your answers to whatever questions you remember and I'll update!
1. NUCLEAR PHYSICS
(State difference between nucleons of 131-I and 125-I) 131 has 6 more neutrons
(What is nucleon number after Beta-minus decay?) 131
(State two differences between nuclei after electron capture) One less proton, one more neutron
(State 3 differences between ____ and Beta-minus decay) Beta-minus changes neutron to proton, Beta-minus emits antineutrino, Beta-minus involves weak interaction
2.
3.
4.
5.
6.
7. ELECTRICITY
(Explain why V1 decreases when brightness of bulb increases)
(Explain why V2 > V1 when identical cell added in parallel)
8. A
9. D
10. C
11. C
12. C
13. A
14. C
15. D
16. D
17.
18.
19.
20.
21.
22.
23.
24.
25.
26.
27.
28.
29.
30.
31.
32. D
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urgurlbecca
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This is what I remember:
1. same answers as you for question one except for the last bit I wrote: the exchange particle is the w boson as opposed to the virtual photon as its weak interaction, beta decay is due to being neutron rich

2.a.) i didnt know what to put, it was an explain how the structure at A (LED to prism) means the ray doesnt deviateand b.) again another explain how the sturcture means the ray doesnt deivate (prism to windscreen)
c.)
d.) i wrote water has a higher refractive index this means the critical angle is higher, less ray is reflected so less reaches detector

i think there was a moments question about how the privot means the tension is unaffected by weight of box for the tension I got around 2000 N dont remember exact value

steel crash barrier over concrete crash barrier i think steel deformed so that meant work was done changing shape of material, less transferred to dummies inside
Last edited by urgurlbecca; 4 weeks ago
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miniwiv
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I got pass, as the car would put 55kn of force into barrier which is less than 60kn it can take but im not sure
(Original post by dansmithson)
What did people get for the steel barrier test: will it pas/fail Q?
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Iapetusss
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For the first part for the MCQs I got ADCCCABDDACCDBBDBAACC
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AlecCoates
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(Original post by dansmithson)
What did people get for the steel barrier test: will it pas/fail Q?
I got that it passed (only ~1.35m deflection out of allowed 1.5m)
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urgurlbecca
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(Describe pattern seen on screen)
its single slit so there would be a wide central maxima of red and green light with alternating dark and red/green fringes i think
(Describe differences when green light replaced by red light)
red has a longer wavelngth so central maxima wider and less intense
(Find order between 1st order and central maximum) 18.1°
(In practice, light is of range 600-700nm. Explain differences.) source is not coherent?? so inteference pattern is a jumble as the waves with bigger wavelgnth get diffracted more etc.
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Ghjkkiggf
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I got that
(Original post by AlecCoates)
I got that it passed (only ~1.35m deflection out of allowed 1.5m)
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Spiket
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1st electricity question: Since the current must be higher the internal resistance is a larger proportion of the total circuit resistance so lost volts increases.

2nd electricity question: as the cells are in parallel the total internal resistance is half the original value so lost volts decreases.
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The_Governor200
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For 2d) woudn't the water having a higher refractive index increase the critical angle not decrease it? I got that for the windscreen and air the critical angle was 41°, but in the presence of a water droplet the critical angle changes to 61° so no total internal reflection takes place?
(Original post by urgurlbecca)
This is what I remember:
1. same answers as you for question one except for the last bit I wrote: the exchange particle is the w boson as opposed to the virtual photon as its weak interaction, beta decay is due to being neutron rich

2.a.) i didnt know what to put, it was an explain how the structure at A (LED to prism) means the ray doesnt deviateand b.) again another explain how the sturcture means the ray doesnt deivate (prism to windscreen)
c.)
d.) i wrote water has a higher refractive index this means the critical angle is lower, angle of refraction is lower and less ray is reflected so less reaches detector

i think there was a moments question about how the privot means the tension is unaffected by weight of box for the tension I got around 2000 N dont remember exact value

steel crash barrier over concrete crash barrier i think steel deformed so that meant work was done changing shape of material, less transferred to dummies inside
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