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AQA Physics PHYA5 - Thursday 18th June 2015 [Exam Discussion Thread] Watch

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    (Original post by gcsestuff)
    " using newtons laws describe how a molecule of gas exerts pressure in a container, while travelling around in a circle with a mass attached to a cone connected to a 30k ohm resistor"




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    Haha, you forgot the metal ring


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    (Original post by gcsestuff)
    Am exciting day of radioactivity lays ahead of me. Oh the joys


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    I share your pain...I'm splitting up each section on unit 5 into mini topics and trying to write down literally everything I know and then comparing it to my notes, radioactivity is today's topic, the joys.
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    (Original post by emu_neutrino)
    I share your pain...I'm splitting up each section on unit 5 into mini topics and trying to write down literally everything I know and then comparing it to my notes, radioactivity is today's topic, the joys.
    All I've got left Is radioactivity and discovery of the electron. Then I think I'm just gonna start again haha


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    (Original post by gcsestuff)
    Am exciting day of radioactivity lays ahead of me. Oh the joys


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    I done that yesterday it's all astro for me
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    If anyone doing Astro could give me a nice summary of Balmer lines for when it doesn't come up in the six mark question I'd really appreciate it!!
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    You do not account for neutron K.E when doing mass defect because you only want to find the change in mass.

    If you find the change in mass and energy it should be zero (conservation of energy).

    So what you do is find the change in mass in total of left hand side and right hand side then that gives you the energy gained (increase in K.E of the neutrons).

    The water serves both as a neutron moderator (it slows down the fission neutrons to thermal energies), and as a heat transfer fluid. So increase in K.E of the neutrons make the water warm up which is (I assume) eventually used to turn turbines.
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    Can someone explain what the link between count rate and Activity is please.
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    (Original post by moeeahmed)
    Can someone explain what the link between count rate and Activity is please.
    Activity is the total number of emissions per second in all directions from the source.

    Whereas if you use a Geiger tube, you will only measure a fraction of this value (count rate).

    both are measured in Bq.
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    I've took the info out of two books and compiled the basic rules.!!!!!! Could someone just check I've got it all the right way round pleaseName:  image.jpg
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    Can someone explain to me electron diffraction in estimating the size of the nucleus thanks


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    How would you answer part b(ii) of this question in the June 2012 paper3 (b) A γ ray detector with a cross-sectional area of 1.5 × 10–3 m2 when facing the source is placed 0.18 m from the source. A corrected count rate of 0.62 counts s–1 is recorded. 3 (b) (i) Assume the source emits γ rays uniformly in all directions. Show that the ratio number of γ photons incident on detector number of γ photons produced by source is about 4 × 10–3.
    3 (b) (ii) The γ ray detector detects 1 in 400 of the γ photons incident on the facing surface of thedetector.Calculate the activity of the source. State an appropriate unit.
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    (Original post by gcsestuff)
    Can someone explain to me electron diffraction in estimating the size of the nucleus thanks


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    So you have a very thin material somewhere.
    You give electrons lots of energy by passing high voltages through them. This gives the electrons a de broglie wavelength of slightly less than the diameter of a nucleus.

    The electron beam is fired at the thin material and then a counter is used to plot a graph of counts against angle some distance behind the thin material. Also might want to mention the electrostatic force is attractive (protons and electrons)

    The angle between the center and the first minimum (theta min) along with the de broglie wavelength of the electron beam is used to get a value of the size of a nucleus.
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    Isn't it electrostatic attraction between the negatively charged electron and the positively charged nucleus?
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    Anyone know of any disadvantages of a CCD?


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    (Original post by moeeahmed)
    Isn't it electrostatic attraction between the negatively charged electron and the positively charged nucleus?
    Yep that's what I meant
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    Can someone give me a brief outline of how a Transmission Electron Microscope works?
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    Name:  image.jpg
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    (Original post by Sbarron)
    Name:  image.jpg
Views: 103
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p_1 V_1 = p_2 V_2

    

\therefore (101 \times 10^{3})(10 \times 10^{-4}) = p_2 (8 \times 10^{-4})

    

p_2 = 126 \times 10^3\ \text{Pa}


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    Thanks I just worked it out another way that took ten times as long lol I started finding the ratio of moles I didn't think I could do it that way because the volume of the tank stays the same
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    (Original post by Sbarron)
    Thanks I just worked it out another way that took ten times as long lol I started finding the ratio of moles I didn't think I could do it that way because the volume of the tank stays the same
    I didn't think of adding the two volumes together for V1
 
 
 
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