AQA Physics PHYA5 - 28th June 2016 [Exam Discussion Thread]

I think it's 1/4 since that's the distance from an antinode to a node

This is what I thought too.

This is 1/4 of a wavelength:


This is 1/2 a wavelength:

Do you rmemeber what the question was asking?

This is what I thought too.

This is 1/4 of a wavelength:


This is 1/2 a wavelength:

Applied physics anyone? What did u get for the efficiency

My turning points answers:

1)
a) Cathode rays are electrons, specific charge was 1800x that of a H+ ion, so mass is very light.
b) Electron beam collides with the gas atoms, causes ionisation, the gas gets excited and then de-excites, emiting photos in the visible light spectrum.
c) 9.1x10^10 for the calculated specific charge.
2
a) 6 marker. Increasing potential difference increases work that needs to be done against the potential difference for electrons to move across the gap, as you increase the potential difference the current will increase. Therefore the kinetic energy of the electrons will be reduced. At the point where current is zero is the stopping potential. Can be used to find the maximum kinetic energy by calculating eV. Einstein's equation is hf = thi + ekmax where ekmax can be replaced by eV and used to find the work function or the frequency.
b) Work function - can't remember.
c) Can't remember what I got here either - 21 or 25?

3)
a Electric field and magnetic field, 180 degrees in phase
b) Increasing the distance means that it reflects back at a different point in the wave cycle, so a different number of wavelengths is reflected back, the phase difference is different and therefore they destructively interfere rather than constructively interfere
c) Should be 0.034m
d) Speed of light is 3x10^8 - I was unsure about this one. Did anyone think it was a poorly worded question? What did they mean by the ORIGINAL assumption that light was electromagnetic? Did that mean the assumption before this experiment, or the very first instance?

4) a) Show that question.
b) Something very small, show that answer from part a * distance * 1000

for the first question, did you use the angle as 42.5? in sintheta

yeah. I'm sure they'll probably take anything between 40 and 45.

Do you remember how many marks was Q1 worth?


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Last question: what was the question for the fission and fusion following the first one about why either are on either side of the graph, the one before working out the mass difference?


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The question about why fusion released more energy than fission?

That was part a, I think. There was one after that and before the Q about mass defect


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I missed all the stuff but nobody seems to do applied here wtf lol
I can't remember any of my answers. I was so desperate to get out of the exam my mind was somewhere else lmao. Prob lost marks for Boyle's law assumption, adding bg radiation back, six marker as always, and some picky ass MS for the fusion/fission business, and a couple on applied due to six mark, but who cares, WE ARE DONE WITH A LEVELS

The questions were from what I can remember in no order:

- Why fission and fusion is restricted to parts of the graph?
- Why fusion releases more energy?
- Mass defect of oxygen?
- The energy released when oxygen forms?
- How can you use the graph to calculate the binding energy of oxygen?

I think your first 2 questions were 1 question?


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