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# OCR PHYSICS B G491~ 19th May 2015 AM ~ AS Physics watch

1. (Original post by HennersPD)
For the bandwidth it was just largest - smallest?
yea 10,000 - 100 = 9900
2. (Original post by MrPenguinPerson)
Okay I think I remember what most of the questions were, but not the answers... anyways this might help

PS, Some of this may be wrong I can't remember completely

SECTION A
Q1 Units (3)
Power AV
Coulomb - As
Conductance - AV^-1

Q2 Refractive Index (2)
3x10^8/1.7= 1.8x10^8

Q3 Potential Divider (2)
3.2 or 4.8 ?

Q4 Bird Chirrup
Aspects of Bird Song Wave (2)
Number of oscillations (2)

Q5 Waveforms of Sounds
Logarithmic scale? (1)
Estimate of highest music frequency (1)
Estimate of bandwidth of human speech (1)

Q6 Lenses
Reading Glasses - Near point/curvature (2)
Reading Glasses - Minimum power (3)

Q7 Current Voltage Resistance
Find average (2)
Find total charge (2)

SECTION B
Q8 Conductance and resistance
Non- ohmic conductor? (1)
I think there was a two marker here but can't remember the question (2)
Find length of wire (3)
Resistivity ratio (2)
Temperature increase effect on resistivity (3)

Q9 Materials
YM Graphs (3)
Calculation of YM (2)
Alloys and Microscopic Properties (6)

Q10 Imaging
Levels=16? (1)
Size of image (2)
Size of video (2)
Magnification (3)
Resolution (2)
Another graph (2)
Graph of AFM (2)
How image is produced (1)
im sure that the aspects of frequency and current was only one mark each
3. (Original post by MrPenguinPerson)
Q4 Bird Chirrup
Aspects of Bird Song Wave (2)
- frequency decreases, then increases sharply
- many tiny frequency fluctuations within it
Number of oscillations (2)
1600
my input
4. (Original post by jpetersgill)
Q3 was a potential divider I'm pretty sure.. But the lens one was 3.2D

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James is that you? Did you really find it hard? Also, can confirm that I got 3.2D, pretty sure that's solid. On the last graphing question - bump goes up to 260 for each, but first a straight line up to 150 on each side due to atoms being a circles so immediately hit half-way up the atom at the diameter - not sure if OCR will penalize not seeing this.
5. (Original post by StrangeBanana)
yea 10,000 - 100 = 9900
i got it as 9.99 x 10^4 :/ so I need 100 x10^3 -100??
6. (Original post by HennersPD)
So did you get 4.8D for the power as u was negative?
(Original post by Alex .G.)
1/1.25 = - 0.8D
ii) power = -0.8 + (ans) = 4. So =4.8D
It's 3.2D.

She's reading the book (or something) at a distance of 0.25m in front of her eyes, so those wave-fronts have a curvature of 1/(-0.25m) = -4D. She needs those wave-fronts to have their curvature increased to -0.8D, as her near point is 1.25m (and 1/(-1.25m) = -0.8D). So the lens needs to have a power of -0.8 - (-4) = -0.8 + 4 = 3.2D.
7. the last graphing question...it was dips not bumps...because at 0.65 nm (0.4nm+0.25nm) the current was less than as 04nm
8. (Original post by HennersPD)
i got it as 9.99 x 10^4 :/ so I need 100 x10^3 -100??
How did you get 9.99x10^4?

(Original post by Jezzer08)
the last graphing question...it was dips not bumps...because at 0.65 nm (0.4nm+0.25nm) the current was less than as 04nm
When the needle goes over the atoms it decreases the distance from 0.4nm to 0.15nm, so it increases the current
9. (I am not giving any guarantee that this is correct. It is based on my faulty memory and the other responses here.)

SECTION A
Q1 Units (3)
Power AV
Coulomb - As
Conductance - AV^-1

Q2 Refractive Index (2)
3x10^8/1.7= 1.8x10^8

Q3 Potential Divider (2)
(4.5 / 280) * 40 = 0.64V

Q4 Bird Chirrup
Aspects of Bird Song Wave (2)
High frequency, followed by low frequency then high frequency again, averaging around 3kHz.
Chirrup lasts 0.5 seconds.
Number of oscillations (2)
3000 oscillations per second * 0.5 seconds = 1500 oscillations.

Q5 Waveforms of Sounds
Logarithmic scale? (1)
Increases by a multiple of 10 each time.
Estimate of highest music frequency (1)
350Hz
Estimate of bandwidth of human speech (1)
10kHz - 100Hz = 9900Hz

Q6 Lenses
Reading Glasses - Near point/curvature (2)
1/1.25 = 0.8D
Reading Glasses - Minimum power (3)
4.0D - 0.8D = 3.2D

Q7 Current Voltage Resistance
Find average current (2)
Average P.D is 2.6 V (52 blocks, *0.5/10 = 2.6V)
Resistance is 5 ohms
V=IR, I = V/R
I = 2.6/5 = 0.52A (will probably accept 0.5A)
Find total charge (2)
10 hours = 36000 seconds.
0.52A
Q =It = 0.52 * 36000 = 18720 (18000 if A = 0.5A)

* I believe there was another question here regarding a description of the effects of temperature, not sure? I think it was a 3 marker, and it basically just wanted a higher temperature means a longer working life time and higher voltages at all times.

=== 20 marks ===

SECTION B
Q8 Conductance and resistance
Non- ohmic conductor? (1)
I is not proportional to V, so resistance isn't constant.
Fill in the table (2)
3.14ohms, 20.somethingohms, something or other Watts.
Find length of wire (3)
0.0018m (awrt 0.002m, 1.8cm).
Resistivity ratio (2)
roughly 6.7
Temperature increase effect on resistivity (3)
Higher temperature leads to more movement of ions which mean that electrons find it harder to move through material. As electrons are charge carriers it means it is harder for them to move through.

Q9 Materials
YM Graphs (3)
D,A,B.
Calculation of YM (2)
Can't remember? I think the answer was 40GPa.
Alloys and Microscopic Properties (6)
For crane - A. Has highest resistance to stress so when under a large stress (ie from a weight attached) will not deform plastically. This is because pinned guest atoms prevent the movement of dislocations.
For crumple zone - D. Least stiff (for this, imagine you have some paper and some titanium. The paper crumples more, and is less stiff). This is due to fewer pinned dislocations (?).

Q10 Imaging
Levels=16? (1)
2^4 = 16
log2(16) = 4
Size of image (2)
500*300*4 = 600,000 bits
= 75000 bytes
Size of video (2)
90*5*75000 = 3.375*10^7 bytes.
Magnification (2)
Can't remember. Something very high.
Resolution (1)
Can't remember. Something very low as far as I can remember.
Calculate sensitivity at 25nm (2)
I got 670pA/nm, but I would assume ±100 or so depending on which gradient you got.
Graph of AFM (2)
Flat lines at 100pA, then curved peaks on dotted lines up to 260pA.
How image is produced (1)
High points are mapped to lighter colours to produce the pattern on the image.

I think this paper was harder than quite a few past papers. Not sure if everything I just typed up was accurate, I have forgotten quite a bit of the paper. Also some of my worded answers aren't very good as I rushed them here. This paper took a little longer than some past papers, I think I finished first pass through in 35 minutes.
10. (Original post by StrangeBanana)

When the needle goes over the atoms it decreases the distance from 0.4nm to 0.15nm, so it increases the current
how does it decrease...im sorry i dont understand
11. (Original post by Jezzer08)
how does it decrease...im sorry i dont understand
Ok so you had a graph of negative gradient of current again nm. When the microscope tip goes over the atom, the distance decreases. As you are now plotting current on your graph, since its a negative gradient when nm decreases, the current increases. Negative gradient is similar to inversely proportion, if you think that way.
12. (Original post by Jezzer08)
how does it decrease...im sorry i dont understand
If you think of a table, and you put some marbles on it which are 2.5cm high, and you move your hand 4cm over the table, when it is not over the table you are 4cm off the surface. When over the marbles you are 4cm-2.5cm=1.5cm from the marble surface. If it increased then the marbles would need to dip.
13. (Original post by ThatPerson2)
(I am not giving any guarantee that this is correct. It is based on my faulty memory and the other responses here.)

SECTION A
Q1 Units (3)
Power AV
Coulomb - As
Conductance - AV^-1

Q2 Refractive Index (2)
3x10^8/1.7= 1.8x10^8

Q3 Potential Divider (2)
(4.5 / 280) * 40 = 0.64V

Q4 Bird Chirrup
Aspects of Bird Song Wave (2)
High frequency, followed by low frequency then high frequency again, averaging around 3kHz.
Chirrup lasts 0.5 seconds.
Number of oscillations (2)
3000 oscillations per second * 0.5 seconds = 1500 oscillations.

Q5 Waveforms of Sounds
Logarithmic scale? (1)
Increases by a multiple of 10 each time.
Estimate of highest music frequency (1)
350Hz
Estimate of bandwidth of human speech (1)
10kHz - 100Hz = 9900Hz

Q6 Lenses
Reading Glasses - Near point/curvature (2)
1/1.25 = 0.8D
Reading Glasses - Minimum power (3)
4.0D - 0.8D = 3.2D

Q7 Current Voltage Resistance
Find average current (2)
Average P.D is 2.6 V (52 blocks, *0.5/10 = 2.6V)
Resistance is 5 ohms
V=IR, I = V/R
I = 2.6/5 = 0.52A (will probably accept 0.5A)
Find total charge (2)
10 hours = 36000 seconds.
0.52A
Q =It = 0.52 * 36000 = 18720 (18000 if A = 0.5A)

* I believe there was another question here regarding a description of the effects of temperature, not sure? I think it was a 3 marker, and it basically just wanted a higher temperature means a longer working life time and higher voltages at all times.

=== 20 marks ===

SECTION B
Q8 Conductance and resistance
Non- ohmic conductor? (1)
I is not proportional to V, so resistance isn't constant.
Fill in the table (2)
3.14ohms, 20.somethingohms, something or other Watts.
Find length of wire (3)
0.0018m (awrt 0.002m, 1.8cm).
Resistivity ratio (2)
roughly 6.7
Temperature increase effect on resistivity (3)
Higher temperature leads to more movement of ions which mean that electrons find it harder to move through material. As electrons are charge carriers it means it is harder for them to move through.

Q9 Materials
YM Graphs (3)
D,A,B.
Calculation of YM (2)
Can't remember? I think the answer was 40GPa.
Alloys and Microscopic Properties (6)
For crane - A. Has highest resistance to stress so when under a large stress (ie from a weight attached) will not deform plastically. This is because pinned guest atoms prevent the movement of dislocations.
For crumple zone - D. Least stiff (for this, imagine you have some paper and some titanium. The paper crumples more, and is less stiff). This is due to fewer pinned dislocations (?).

Q10 Imaging
Levels=16? (1)
2^4 = 16
log2(16) = 4
Size of image (2)
500*300*4 = 600,000 bits
= 75000 bytes
Size of video (2)
90*5*75000 = 3.375*10^7 bytes.
Magnification (3)
Can't remember. Something very high.
Resolution (2)
Can't remember. Something very low as far as I can remember.
Calculate sensitivity at 25nm (2)
I got 670pA/nm, but I would assume ±100 or so depending on which gradient you got.
Graph of AFM (2)
Flat lines at 100pA, then curved peaks on dotted lines up to 260pA.
How image is produced (1)
High points are mapped to lighter colours to produce the pattern on the image.

I think this paper was harder than quite a few past papers. Not sure if everything I just typed up was accurate, I have forgotten quite a bit of the paper. Also some of my worded answers aren't very good as I rushed them here. This paper took a little longer than some past papers, I think I finished first pass through in 35 minutes.
Hi for crumple zone alloy B would be used because it is tough and absorbs a large amount of energy before breaking plastically, so this would reduce the impact of crash
14. (Original post by RobTyrrell)
.
Yeah - and I thought it was a relatively hard paper, not saying I thought I did badly in it

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15. What was the estimate the average pd question?

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16. (Original post by Wolfea)
For the ratio I think I got 6.6..that's about as much as I can remember
Yeah I got 6.7 so sounding along the right lines...
17. (Original post by Zain.chishty)
Hi for crumple zone alloy B would be used because it is tough and absorbs a large amount of energy before breaking plastically, so this would reduce the impact of crash
Ah ok then, you might be right. I just assumed it as D because it was the least stiff, and I was thinking of crumpling stuff. Who knows :P.
18. I'm sure the highest frequency was 100kHz not 10kHz?? Thats what i put anyway as it dipped a bit but was still the largest freq. present so i did 100,000 - 100 = 99,900 Hz ~ 100,000Hz?
19. (Original post by ThatPerson2)
Ah ok then, you might be right. I just assumed it as D because it was the least stiff, and I was thinking of crumpling stuff. Who knows :P.
I was torn between B and D, but went for D; same reason as yourself... I imagine if you justify your choice both are worth at least some marks. Here's hoping anyway...
20. (Original post by Mik3yMcFly001)
I was torn between B and D, but went for D; same reason as yourself... I imagine if you justify your choice both are worth at least some marks. Here's hoping anyway...
I just assumed that given the idea of a crumple zone is to... well crumple, you would want it to not be very stiff - I mean a material with a YM like A may have a very long plastic region, but it wouldn't work as a 'crumple zone' I therefore thought it would be the one which would crumple most easily, ie the least stiff. I will ask my physics teacher about it and see what he says.

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