IB Physics HL P1/P2

[Sandy]

59 minutes ago, iblearner said:

There was a mistake in the paper too, i think. A lot of people think, including myself, that they hadn't given us the value of D in the wave question in paper 2. 

I thought the same but then I applied the n*lamda*=dsin*theta* formula and got an answer

[Sandy]

2 minutes ago, thecsstudent said:

Does anyone know what the graph was like in the capacitor question of Voltage vs time?

If I'm not wrong, it was a decreasing function. As the given graph increased, the graph you had to make decreased.

[thecsstudent]

Just now, Sandy said:

If I'm not wrong, it was a decreasing function. As the given graph increased, the graph you had to make decreased.

yay i did the same. Let's hope it's correct.

[Sandy]

2 minutes ago, thecsstudent said:

yay i did the same. Let's hope it's correct.

Did you get time to go through the whole paper?

[thecsstudent]

Just now, Sandy said:

Did you get time to go through the whole paper?

you mean to attempt all the exercises? All except for the one on topic 8 and i left several other sub-questions unanswered. you?

[Guest iblearner]

9 minutes ago, Sandy said:

I thought the same but then I applied the n*lamda*=dsin*theta* formula and got an answer

oh okay lol is it correct? idt they gave the value of theta iirc

[Sandy]

4 minutes ago, thecsstudent said:

you mean to attempt all the exercises? All except for the one on topic 8 and i left several other sub-questions unanswered. you?

I left the last question and a few other subparts

[Sandy]

2 minutes ago, iblearner said:

oh okay lol is it correct? idt they gave the value of theta iirc

I think we had to find it in another subquestion. Or I found it for that question specifically. Idr the values but that's what I did. Hoping its correct!

[Odelouche]

Hey guys, 

A couple comments about that exam: first of all, TZ0? From what I know, everyone in the world got the same paper, including South America. Is this normal when they change the syllabus? There were several parts that I couldn't do, but I'm that was because of lack of understanding or knowledge. However, there are a few legitimate doubts I have about some questions.

First, when they gave you a nuclear reaction (can't remember the element, but the nucleon number was 32) and asked you to find the emitted energy? The mass of the daughter nucleus was larger than the mass of the reactant nucleus... Which implies an absorption of energy, not a release? Or did I miss something?

Second, in the greenhouse effect question, for the second subpart, you had the amount of incident power on the outer atmosphere of Earth coming from the sun (1400W/m²), as well as the albedo of the Earth, 0.3 (albedo = scattered power/incident power). So you multiply 0.3*1400 to give you 420W/m² of scattered power. Incident power - scattered power = absorbed power right? So 1400 - 420 = 980W/m²? But they wanted us to arrive at 245W/m², which required us to divide 980 by 4, which I reluctantly did "for science" but without any understanding... Did I miss something, or are they wrong? 

Finally, every single person I've talked to about the HL exam said they had no idea how to do the last subpart of the exam, which required you to find the energy in Mev of an alpha particle emprisoned inside a gold nucleus, using Heisenberg's uncertainty principle. ???? First of all, in the uncertainty principle, energy is paired with time, which we do not have? Second, as its name suggests, the uncertainty principle deals with uncertainties, not actual values? And third, it's an inequality? Again, what am I missing here? 

I lost around 21 marks with absolute certainty, 30 marks with a conservative estimate of how mad it could go. The 7 is still in reach, praying for those mark bands to feel the force of gravity... Btw, did they just suddenly decide to remove all questions asking for definitions?? Or was that something they've announced? 

 

P.S: As I was writing this, I suddenly thought of something for this last subpart... We know the maximum allowed range of motion inside the nucleus of gold for the alpha particle (don't ask me how it got there) must be twice the radius of that nucleus (or the diameter), which was previously taken to be the least distance of approach, in the first part of the question. We use that as the uncertainty in position, considering the strong nuclear force and electromagnetic force must be bouncing that alpha particle everywhere inside that nucleus. Using Heisenberg's principle, we get an inequality for the uncertainty in momentum. Divide the whole thing by the mass of the alpha particle, you get it's minimum velocity, which you can then convert back to Mev through the equation for kinetic energy. It still only gives you an inequality, but maybe they're looking for the least possible energy of the alpha particle? 

[josephapakesch]

3 hours ago, Animate said:

Paper 1 was harder than usual. Paper 2 was just flat out insane. We're IB students, not quantum physicists.

I totally agree. For example in standard they asked as why quarks were theoretical hypothesis before being experimentally proven as a three mark question. How am i supposed to know that. I studies physics, not the history of it...

[theredviper]

in SL, what on earth was the quark question near the end: "explain why quarks were developed and organised etc.". I mean wtf its supposed to be a physics exam not a stupid history lesson!

Edited May 7, 2016 by theredviper
Damn, i just saw the above reply -_-

[AA21]

I suppose as people are talking about the SL paper here I'll just join in, I don't really want to start a separate discussion. 

I felt the paper was absolutely horrendous. It was my first time going into a physics exam feeling fully prepared. I have been getting 6's and 7's in past tests and I really felt I could pull a nice 7 for this one. I left the exam room crying after paper one. I was extremely shocked and overwhelmed by the 'trickiness' of the questions. I believe a lot of my classmates agreed with me by saying it wasn't so much that the paper was on syllabus topics that we've never heard of. Yes there was Newton's laws, kinematics, waves, solar power/radiation, quantum physics. However, it was the TYPE of questions from each topic that really threw me off. Paper 1 took me so long to answer because I had to analyse each questions so thoroughly in order to understand it (many of which I didn't!!) They really twisted those questions, similar situation in paper 2. 

All in all, it was an extremely disappointing paper. I did not feel prepared AT ALL for what I went through in that exam room. 

[thecsstudent]

1 hour ago, Odelouche said:

Hey guys, 

A couple comments about that exam: first of all, TZ0? From what I know, everyone in the world got the same paper, including South America. Is this normal when they change the syllabus? There were several parts that I couldn't do, but I'm that was because of lack of understanding or knowledge. However, there are a few legitimate doubts I have about some questions.

First, when they gave you a nuclear reaction (can't remember the element, but the nucleon number was 32) and asked you to find the emitted energy? The mass of the daughter nucleus was larger than the mass of the reactant nucleus... Which implies an absorption of energy, not a release? Or did I miss something?

Second, in the greenhouse effect question, for the second subpart, you had the amount of incident power on the outer atmosphere of Earth coming from the sun (1400W/m²), as well as the albedo of the Earth, 0.3 (albedo = scattered power/incident power). So you multiply 0.3*1400 to give you 420W/m² of scattered power. Incident power - scattered power = absorbed power right? So 1400 - 420 = 980W/m²? But they wanted us to arrive at 245W/m², which required us to divide 980 by 4, which I reluctantly did "for science" but without any understanding... Did I miss something, or are they wrong? 

Finally, every single person I've talked to about the HL exam said they had no idea how to do the last subpart of the exam, which required you to find the energy in Mev of an alpha particle emprisoned inside a gold nucleus, using Heisenberg's uncertainty principle. ???? First of all, in the uncertainty principle, energy is paired with time, which we do not have? Second, as its name suggests, the uncertainty principle deals with uncertainties, not actual values? And third, it's an inequality? Again, what am I missing here? 

I lost around 21 marks with absolute certainty, 30 marks with a conservative estimate of how mad it could go. The 7 is still in reach, praying for those mark bands to feel the force of gravity... Btw, did they just suddenly decide to remove all questions asking for definitions?? Or was that something they've announced? 

 

P.S: As I was writing this, I suddenly thought of something for this last subpart... We know the maximum allowed range of motion inside the nucleus of gold for the alpha particle (don't ask me how it got there) must be twice the radius of that nucleus (or the diameter), which was previously taken to be the least distance of approach, in the first part of the question. We use that as the uncertainty in position, considering the strong nuclear force and electromagnetic force must be bouncing that alpha particle everywhere inside that nucleus. Using Heisenberg's principle, we get an inequality for the uncertainty in momentum. Divide the whole thing by the mass of the alpha particle, you get it's minimum velocity, which you can then convert back to Mev through the equation for kinetic energy. It still only gives you an inequality, but maybe they're looking for the least possible energy of the alpha particle? 

What I did for the Heisenberg uncertainty question was:

We know that Kinetic energy = p^2/2m (from the booklet)

In this case p is approximately equal to Δp (the uncertainty in p) and Δx is half the radius so we can take a rough equality for the uncertainty principle to find Δp and then substitute it into the kinetic energy formula.

The whole thing is based on rough equalities. I wouldn't have known that but thankfully the book that I used had a very similar example so I remembered it.

Edited May 7, 2016 by thecsstudent

[Basil]

2 hours ago, iblearner said:

Sure, no question was beyond the syllabus. But the questions were difficult. They were harder than we expected. 

Judging from your reply, you must have aced the exam. Well, good for you. 

Braj p1 had a q about rotational dynamics, not in the syllabus

[thecsstudent]

1 minute ago, Basil said:

Braj p1 had a q about rotational dynamics, not in the syllabus

i don't think it was rotational dynamics, it was circular motion which is in topic 6.

[LolzDoingIB]

I have not sat this exam but it sounds like it was difficult! What was so difficult about it? Any questions that were particularly difficult?

[NickyJo]

1 hour ago, Odelouche said:

Hey guys, 

A couple comments about that exam: first of all, TZ0? From what I know, everyone in the world got the same paper, including South America. Is this normal when they change the syllabus? There were several parts that I couldn't do, but I'm that was because of lack of understanding or knowledge. However, there are a few legitimate doubts I have about some questions.

First, when they gave you a nuclear reaction (can't remember the element, but the nucleon number was 32) and asked you to find the emitted energy? The mass of the daughter nucleus was larger than the mass of the reactant nucleus... Which implies an absorption of energy, not a release? Or did I miss something?

Second, in the greenhouse effect question, for the second subpart, you had the amount of incident power on the outer atmosphere of Earth coming from the sun (1400W/m²), as well as the albedo of the Earth, 0.3 (albedo = scattered power/incident power). So you multiply 0.3*1400 to give you 420W/m² of scattered power. Incident power - scattered power = absorbed power right? So 1400 - 420 = 980W/m²? But they wanted us to arrive at 245W/m², which required us to divide 980 by 4, which I reluctantly did "for science" but without any understanding... Did I miss something, or are they wrong? 

Finally, every single person I've talked to about the HL exam said they had no idea how to do the last subpart of the exam, which required you to find the energy in Mev of an alpha particle emprisoned inside a gold nucleus, using Heisenberg's uncertainty principle. ???? First of all, in the uncertainty principle, energy is paired with time, which we do not have? Second, as its name suggests, the uncertainty principle deals with uncertainties, not actual values? And third, it's an inequality? Again, what am I missing here? 

I lost around 21 marks with absolute certainty, 30 marks with a conservative estimate of how mad it could go. The 7 is still in reach, praying for those mark bands to feel the force of gravity... Btw, did they just suddenly decide to remove all questions asking for definitions?? Or was that something they've announced? 

 

P.S: As I was writing this, I suddenly thought of something for this last subpart... We know the maximum allowed range of motion inside the nucleus of gold for the alpha particle (don't ask me how it got there) must be twice the radius of that nucleus (or the diameter), which was previously taken to be the least distance of approach, in the first part of the question. We use that as the uncertainty in position, considering the strong nuclear force and electromagnetic force must be bouncing that alpha particle everywhere inside that nucleus. Using Heisenberg's principle, we get an inequality for the uncertainty in momentum. Divide the whole thing by the mass of the alpha particle, you get it's minimum velocity, which you can then convert back to Mev through the equation for kinetic energy. It still only gives you an inequality, but maybe they're looking for the least possible energy of the alpha particle? 

I did the same exact thing for the greenhouse one!! everyone was telling me that the answer shouldn't have been 420, but they later said they didn't even attempt that question because it didn't give the radius of the earth. was the radius of the earth even applicable to the question????

as for Heisenberg uncertainty, I wrote in a random equation and hope they give me method marks. it was extremely heavy on nuclear physics!! did the syllabus say to only spend two hours on it? 

[Someone]

1 hour ago, NickyJo said:

I did the same exact thing for the greenhouse one!! everyone was telling me that the answer shouldn't have been 420, but they later said they didn't even attempt that question because it didn't give the radius of the earth. was the radius of the earth even applicable to the question????

as for Heisenberg uncertainty, I wrote in a random equation and hope they give me method marks. it was extremely heavy on nuclear physics!! did the syllabus say to only spend two hours on it? 

That question was relatively easy the area hit by the sun was pi*r^2 and the area of the planet was 4*pi*r^2. Therefore when dividing those two to find the average radiation, the r^2 could be eliminated and there was no need for the radius of the earth.

To be fair I found other questions such as the diffraction one and the electricity one harder. Which peaks did you use the high ones or the low ones for the graph on the diffraction grating graph? Was I being stupid? Sorry, I didn't really study very much.

[Guest SNJERIN]

27 minutes ago, Someone said:

That question was relatively easy the area hit by the sun was pi*r^2 and the area of the planet was 4*pi*r^2. Therefore when dividing those two to find the average radiation, the r^2 could be eliminated and there was no need for the radius of the earth.

To be fair I found other questions such as the diffraction one and the electricity one harder. Which peaks did you use the high ones or the low ones for the graph on the diffraction grating graph? Was I being stupid? Sorry, I didn't really study very much.

For the four slit experiment, they asked you to deduce the wavelength of light from the graph. To do that you would need to look for the section on the graph for which the first minimum of the single slit diffraction pattern modulate the 4 slit interference pattern. As far I as I remember, that min point occurred at θ ≈ 0.45. Now what you do is to use the formula θ =  λ/d. The gave you d = 10^-6. Thus you just substitute to get λ 4.5*10^-7m and you got the answer. 

[Guest iblearner]

34 minutes ago, Someone said:

That question was relatively easy the area hit by the sun was pi*r^2 and the area of the planet was 4*pi*r^2. Therefore when dividing those two to find the average radiation, the r^2 could be eliminated and there was no need for the radius of the earth.

I did the same thing, but didn't arrive at the answer they wanted.