AQA A Level Physics PAPER 3 3rd june 2019 Unofficial Mark scheme

8900 over here! Rounding errors, perhaps?

Anyone else say use a level for making sure the tube was vertical?

I said use a spirit level

So did i, think that's better than set square like what Hamza said cos of floor not necessarily being level

I got that too I left it as fractions and rounded nothing, got something like 8940... Or 8904 something like that

Anyone else get these?

5 routes
A, B, I (felt very decision-mathsy, did that one!)
k = 1.9*10^5 Bq mm^2
e = 30 mm

lambda = 4.50*10^-3 s^-1
T_1/2 = 154 s
Unit: N m^-2 s
Percentage uncertainty: 19.8 %

EDIT: Just changed the unit; had originally said N m^2 s^-1.

f = 61 Hz (from time period of 16.4 ms)
d = 57.8 cm, giving lambda = 1.16 m
c = 70 m s^-1 (or 71 m s^-1)
mu = 9.9*10^-4 kg m^-1
Diameter = 0.71 mm
Density: rho = 8.9*10^3 kg m^-3

Obviously not everyone will have done Astrophysics, so I'll put those in another post.

What did you guys get for the frequency because I’m sure I got 50 something hertz as opposed to what they’re listing and like 63 ms for c or 68

I got the same values for a lot of these esp, e and k and % unct! but i think i must have got my units messed up for the frequency question as i recall putting something like 650 Hz probs used the wrong scaling factor oopsies

can you send the link for the astro markscheme?

what do you guys think the grade boundaries for paper 3A is gonna be? I'm praying it's the same as the 2017 grade boundaries or lower cause that paper was 🤢.

If I got the frequency wrong would I get ecf cos I used the right methods for the other questions??

I still haven't posted my Astro answers yet, so I guess that now's as good a time as any!

Blue light retracts more than red light.

Concave primary mirror; convex secondary mirror (second or third box).

Gamma A is larger by Stefan's Law (similar T, more negative M, so greater P, and hence larger surface area and diameter).

6-marker conclusion: Telescope A (optical reflector) would give a more detailed image, as its minimum angular resolution is lower (by the Rayleigh criterion). The image might be fainter, though, as smaller diameter gives lower collecting power.

Used m-M = 5log(d/10) to get something like 3.5 or 3.8 pc (can't remember exactly).

H-R scale: 15 at bottom; -10 at top.
Sun at about T = 5700 K and M = 4.83.
Sun goes to giants then dwarfs.
P at right-hand side of giants.

Black hole too dark and cold; supernova too bright. Therefore neither can be plotted on H-R diagram.

Hubble's Law not supported, as z/d not constant (7.06*10^-11 and 9.375*10^-11).

I spoke about relativistic effects for difficulty in quasar measurement, as redshift is not equal to -v/c if v is close to c.

Let me know of any questions I've forgotten, and/or anything you disagree with!

Hubble law was supported by first data, not second galaxy I think. I used v=HD and did all the long calc, think I was right

@Evil Homer
welcome lads

We all know that was clapped so let’s get on with the task

1.1 Precautions when using source of radiation [2 marks]

1.2 determine how many ways A goes to K [1 mark]

1.3 determine how many paths A and M lie in the path of decay of Ra to Pb [3 marks]

1.4 Diagram with aluminium graph on opposite page find minimum thickess, [2 marks]
got 11mm from graph but Beta would travel through 11mm so to stop it i put 12mm
Water measuring question

1.5 y+e = sqrtk/sqrtA [5 marks]
make in y = mx+c
find gradient, sub a pair of coordinates from the graph
k = smth big like 1.8x10^5 mm2Bq^1

1.6 find e [2 marks]
y intercept using similar triangles i got -29...smth

2.1 Percentage uncertainty given d % and L% and gradient ie Q/h was 6.4% [2 marks]
i remember being confused about the n rearranging
19.8%


2.2 units of the weird N symbol [1 marks]
Second box I think Nm-2s

2.3 method of measuring Q, including reduction of uncertainties [4 marks]
use measuring cylinder start stop clock for 1 minute measure volume of water in cyclinder, Q=volume/60
uncertainty reduction: time for longer period, reduces % uncertainty in T as well as Measurement of q because q would also be greater, use a more graduated cylinder

2.4 deadass graph question show decay constant is 4.5x10^-3(even tho it said show it still gave answer space?) [2 marks]
spent a full 7 minutes on this question, tried finding half life then saw the next questions wanted the half life wtf
then did smth with the intercepts and gradient etc then subbed into another equation that got me 4.49x10^-3

2.5 find half life [1 mark]
ln2 / decay constant = 154 seconds
possible ecf for this from part Q2.4

2.6 how to make sure tube was vertical [1 mark]
the CLASSICAL set square-ruler combo

2.7 tube is now angled at 30degrees draw the graph [2 marks]
no clue here i did smth times sin(30) n drew a more steeper line although this is probably wrong

3.1 vernier caliper diameter of rod [1 mark]
0.71mm

3.2 how you'd reduce random error in result of diameter[2 marks]
measure at different points along rod take average exclude anomalies blah blah
reduces random error

Random questions from memory
find frequency from graph [2 marks]
63Hz using the time base from graph (8 small divisions = 1.6cm = 0.016s time period)

find wavelength of wire across bridge [2 marks]
got 57.8cm then doubled to get 1.16m

speed of wave from the data we calculated [1 mark]
c = 70 m s^-1 (or 71 m s^-1)

find mu [3 marks]
use harmonics formula f=1/2Lsqrt(t/mu)
mu = 9.9*10^-4 kg m^-1

find density of the object final question [3 marks]
mu = 9.9*10^-4 kg m^-1
Diameter = 0.71 mm
Density: rho = 8.9*10^3 kg m^-3