AQA Physics Unit 1 PHYA1 20th May 2013

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Reply 1020

Tuya

Any guesses on the full ums boundary?

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Reply 1021

Zakee

Original post by GeneralOJB

The RMS value - 45v.

I had the RMS as 45.3V.

Do you think that will be okay, because all my derived data which gave non exact answers were given to 3 significant figures.

Reply 1022

CR95

Original post by Notorious544d

For the oscilloscope question, I did 20v per division not 16v. Will they both be accepted, so like in the mark scheme, will it say 'accept any sensible value?' I'm guessing the main thing about the question was that you had to write that the time base had to be set at 2ms per division so that the two cycles can be seen. Hmm...

i was going to put 16 but then put 20 because i wrote this way the oscillation can be viewed whilst still having a suitable scale or something like that. I think its possible they could reject 16 and only allow 20 because of that but im not sure

Reply 1023

lebron_23

For the question where it asked to say how you would change the time base blah blah blah, I wrote that I would half the time base as frequency is inversely proportional to the time period and so by halving the time period, the frequency would be doubled. Anyone know if that's the right answer or if it was just a load of crap. Seeing you guys talking about 2ms is making me nervous :eek:

Also, where was the line for the rms thing supposed to go? I put it at 46...

Reply 1024

CR95

Original post by Tuya

Any guesses on the full ums boundary?

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i think 67-68

Reply 1025

Zakee

Original post by CR95

i think 67-68

Mhm, I agree.

Reply 1026

GeneralOJB

Original post by Zakee

I had the RMS as 45.3V.

Do you think that will be okay, because all my derived data which gave non exact answers were given to 3 significant figures.

Yeah I got 45.25, I just rounded down.

Reply 1027

Surf

Original post by Ryejd

mass of electrons is negligible, not once have I seen you have to include their masses.

Isn't that because they usually ask you to find the specific charge of the nucleus??? Today they asked you to find the specific charge of the ion...

Reply 1028

westarmy

Original post by Zakee

Mhm, I agree.

66 No? ;(

Reply 1029

GeneralOJB

I'm guessing 69-70 for full UMS.

Reply 1030

x-Sophie-x

For the oscilloscope question, I said adjust the time base so that the period is 5ms. Would this get me any marks?

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Reply 1031

Tuya

Ouch, I hope 67 and I don't lose any other marks! As the oscilloscope bit was pathetically worded

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Reply 1032

Zakee

Original post by Surf

Isn't that because they usually ask you to find the specific charge of the nucleus??? Today they asked you to find the specific charge of the ion...

You're right. What's funny though is that even if you include the mass of the electrons, the difference in mass is almost infinitesimal. So you'd yield the same answer as if someone included it.

Reply 1033

Xiomara

Original post by Ali_Ludley

I did that as well, 20Vdiv^-1 but I stupidly put 0.5msDiv^-1 instead of 2msDiv^-1 :argh:

I did that too :frown:

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Reply 1034

Tuya

Original post by GeneralOJB

I'm guessing 69-70 for full UMS.

No it's never even been above 66, doubt we will have a change, I'm guessing 67 maybe?

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Reply 1035

ShutUpLegs

Original post by lebron_23

That's what wave theory would say, but if the frequency were to remain above the threshold frequency, surely the emission of electrons wouldn't be affected at all? I mean, the only thing that ever changes anything is the intensity, and it only changes the rate of emission at that.

I thought the reason it was maximum kinetic energy was because the ones further from the metal's surface would need to absorb higher frequency photons to escape so the ones with maximum KE are near surface. Surely decreasing frequency meant the ones in the metal deeper in would need more energy to escape and so their emission would be more frequent for higher frequencies?

Reply 1036

GeneralOJB

Original post by Surf

Isn't that because they usually ask you to find the specific charge of the nucleus??? Today they asked you to find the specific charge of the ion...

Well if you found the specific charge of the nucleus the charge wouldn't be -3.2x10^-19, it would be +3.2x10^-18. :tongue:

Reply 1037

FrankB3

Original post by GeneralOJB

Both. The question that asked you to draw on figure 2 the equivalent DC with the same rate of energy dissipation yadda yadda, was just asking you to draw the RMS line.

Ah, thanks for clearing that up! I did that eventually but I remember seeing like this thing on salters or Antonine that said that the DC line would be above the crest of the wave and it really confused me.

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Reply 1038

GeneralOJB

Original post by SamHedges

The frequency of the photons are all the same, it was monochromatic light. There's a max KE as the electrons nearest to the surface only require the work function (minimum energy) to be removed. The one's deepest in the metal will require more energy and have a lower KE.