don't know what to think really. it was easy at the start then after the graph question section b got harder for me and i didn't know some of the section c questions especially the last one

Reply 168

Mabes

I messed up the red and green light q, but apart from that I thought it was ok.
I'd done quite a lot of practise for the pre-release so found most of Section C straightforward

Reply 169

juniorx

Original post by Mabes

I messed up the red and green light q, but apart from that I thought it was ok.
I'd done quite a lot of practise for the pre-release so found most of Section C straightforward

i didn't even understand what to do for that question. I just calculated the reduce voltage and energy output and then the energy of the red and green light. I didn't even know what to say

Reply 170

Mabes

The fact that it was an LED didn't register, and I said the green light was absorbed by the diffraction grating!
Apparently it was to do with the green light not having the energy to leave the LED or something

Reply 171

m00c0w

Original post by Mabes

Yeah that's what I got. The total energy carried by each electron at 2.1V wasn't enough for green photons, but was enough for red photons.

Overall, I'm pretty damned happy with that exam!

Reply 172

Bloxorus

I thought that was a very good exam. Not hard at all really apart from some of the section c!

Posted from TSR Mobile

Reply 173

juniorx

what did people draw for the velocity/time graph

Reply 174

Mabes

Start of unofficial mark scheme:
Italics are question descriptions, not answers

Section A

1) Nm, Js^-1, kgms^-2
2) A, C, D
3)
4)
5)
6)

Section B

7)
8)
9)
10)

Section C

11) a) sensitivity between 10-20 degrees
5.6 for sensor A
2.4 for sensor B
Unit mV/0C

b) Sensor A: higher sensitivity over this range
c) Sensor B: constant sensitivity over whole range
d)

12)
a)
b)
c)i) experimental factors affecting g
ii) Friction -> reduces g value
Underestimate of ramp length -> increases g value
Overestimate of ramp length -> decreases g value
Average velocity recorded when card went through the light gate despite it accelerating

13) a)i) 0.5s (or anything similar, it was an estimate of reaction time)
ii) speed of light calculation
iii) speed of light is very small fraction of reaction time so is unmeasurable. Can only say that light travels faster than 6.4km/s (using my values).

b)i)
ii) small % uncertainty so small
iii)
iv) underestimated the uncertainty because the difference in values =118 which is much larger than 50

c)i) 1cm uncertainty from the drawing...
ii) 2.94x108 uncertainty of 0.49x108

Feel free to add, I can't remember much more!

(edited 10 years ago)

Reply 175

m00c0w

Original post by Mabes

Start of unofficial mark scheme:
Italics are question descriptions, not answers

Section A

1) Nm, Js^-1, kgms^-2
2) A, C, D
3)
4)
5)
6)

Section B

7)
8)
9)
10)

Section C

11) a) sensitivity between 10-20 degrees
5.6 for sensor A
2.4 for sensor B
Unit mV/0C

b) Sensor A: higher sensitivity over this range
c) Sensor B: constant sensitivity over whole range
d)

12)
a)
b)
c)i) experimental factors affecting g
ii) Friction -> reduces g value
Underestimate of ramp -> increases g value
Overestimate of ramp -> decreases g value

13) a)i) 0.5s (or anything similar, it was an estimate of reaction time)
ii) speed of light calculation
iii) speed of light is very small fraction of reaction time so is unmeasurable. Can only say that light travels faster than 6.4km/s (using my values).

b)i)
ii) small % uncertainty so small
iii)
iv) underestimated the uncertainty because the difference in values =118 which is much larger than 50

c)i) 1cm uncertainty from the drawing...
ii) 294x108 uncertainty of 49x108

Feel free to add, I can't remember much more!

Wouldn't the last question be 2.94 and 0.49? You might want to make a new thread with this.

Reply 176

Mabes

Original post by m00c0w

Wouldn't the last question be 2.94 and 0.49?

Yep, I'll change it.

Reply 177

m00c0w

Original post by Mabes

Start of unofficial mark scheme:
Italics are question descriptions, not answers

c)i) experimental factors affecting g
ii) Friction -> reduces g value
Underestimate of ramp length -> increases g value
Overestimate of ramp length -> decreases g value

Feel free to add, I can't remember much more!

Wouldn't another answer for cii be the an average velocity was recorded when the card went through the light gate despite it accelerating. Furthermore, I'm not sure whether the ramp length would count as it asked for experimental errors, and isn't the ramp length a systematic error? Might be wrong though.

Reply 178

Mabes

Original post by m00c0w

You might want to make a new thread with this.

I would, but there's hardly any of us taking this spec so I don't see much point

Reply 179

m00c0w

Original post by Mabes

I would, but there's hardly any of us taking this spec so I don't see much point

True, but it might be nice for the few of us that do have the spec to have a dedicated thread for the mark scheme so people don't have to sift through the thread, trying to find the mark scheme