Beta Balloons

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    • #44518
      Profile photo of Andrew Normand

      @janicechambers Hi Janice, you mention in the group for the SPN Cambridge Summer School that you have trialled some of the radioactivity workshop ideas.

      Here is an idea I use with Beta Balloons.

      I first write on two pieces of paper, neutrino and positron on them. You could have anti-neutrino and beta particle if preferred. I am using a red balloon for a proton and a blue balloon for a neutron.



      Next screw up the bits of paper into balls and place in the red balloon first.



      Then push the deflated blue balloon into the red balloon. I find you need a balloon pump for this or swimmers lungs.
      You then inflate the blue balloon, but not fully just so it is a reasonable size but less than fully inflated.
      you then push this into the red balloon and inflate the red balloon using a balloon pump with the inflated blue balloon inside.




    • #44520
      Profile photo of Andrew Normand

      Thank you! Just given it a go – success!

    • #44521
      Profile photo of Andrew Normand

      that’s pretty cool – will squeeze it in the radiation course I do.

    • #44545
      Profile photo of Andrew Normand

      I usually do this with my A level students when we do particle physics.

      power point

      With GCSE students doing fusion in stellar cores, you can show them the proton chain mechanism for fusing hydrogen into helium. It is also a great way to talk about isotopes of hydrogen in the chain.


      Student then hold the six protons. Two of the balloons have the blue balloon neutron, positron and neutrino in them.  These students then wander around. Students should wear safety glasses.



      Two students bring their balloons together. This needs to happen in two sets, and one of the balloon in each set must have a blue balloon inside it.


      The two sets of fused protons then have a beta plus decay turning one proton to a neutron. (Warn the student you are going to pop the balloon, students should be wearing safety glasses)


      Then the other two protons fuse to make two helium 3 nuclei


      The two helium 3 collide


      Then two protons move away and a helium 4 nucleus is formed.




      I have always found students like to follow this process.


    • #44563
      Profile photo of Andrew Normand

      That’s a really nice approach. I saw this done for Beta decay by Colin at Exeter’s IOP day last June.

      The only problem I can see with Beta+ decay is that the proton looks more massive than the neutron it decays into with the balloons demo. Do students often ask about this?

    • #44564
      Profile photo of Andrew Normand

      Hi Alessio, There is a lot to discuss with students around this point (No pun intended).  I love telling students that an electron is a point-like particle in the standard model. The classical electron radius is based on its charge and hence its interaction with colliding particles. Again for the Proton and neutron the concept of size for these quantum mechanical objects is meaningless in the usually sense of volume occupied. The quarks that make a nucleon are point-like and are smeared out in space with the surround virtual quarks and gluons that are part of the strong interaction. (This gives the composite hadrons most of their mass).

      In nuclear physics you have a measure of something like size with the unit barn, which is like a cross sectional area of possible interaction for an incident particle. Physicists tend to trow a particle at another to judge it size. These method tends to work better for charged particles for two reasons, the interaction itself and it is easier to hold a charged particle in one place. As you would expect it is also more complicated than this as the size or more correctly the cross sectional area of interaction varies with the incident particles energy. I looked up that a neutron between 10 eV and 1 MeV thrown at a U235 nucleus can experience between 1 to a few thousand barn differences.


    • #44566
      Profile photo of Andrew Normand

      I don’t know if it might be helpful with getting students to appreciate scale but I modified for school an idea I once saw in a televised lecture.


      Our labs are mostly 10-12 metres square so I have one of those ball pen playballs they have for nursery schools suspended in each lab. When discussing atomic theory the teacher can point to it explaining that if the lab were an atom we have in the centre a scaled representation of the nucleus.

      They then point out it isn’t the ball, but the 0.5mm diameter nylon fishing line that supports it (that they can’t usually even see) that is to scale for the diameter of the nucleus.

    • #44572
      Profile photo of Andrew Normand

      That makes sense Dave and it a really nice explanation for the students to appreciate. I would imagine that most think of protons and neutrons as actual ball-like objects.

      Nick, I love your scale of the atom demo. Really powerful!


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