Talking Physics

Diffraction 5 Pound Note

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This topic contains 13 replies, has 3 voices, and was last updated by  Nick Mitchener 2 years ago.

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  • #44942
    Profile photo of Andrew Normand

    Some time ago we had a thread on the diffraction pattern used as a security feature in a Canadian dollar.

    Canadian dollar 1

    Here is an image I took when shining a red laser through the note.

    There was a great video shared on here.

    I tried a laser through the new 5 pound note

    diffraction 5 pound

    You can see the queen is made of little plastic dots on clear plastic
    Queen 2The region that I got the best diffraction from was under the Queen’s chin and you can see the ordered spacing that created it here

    chin china me 2

  • #44943
    Profile photo of Andrew Normand

    it’s rubbish isn’t it compared to the Canadian one? I was very disappointed when I tried it. Will be sticking to Canadian notes for demos.

  • #44991
    Profile photo of Andrew Normand

    Where did you get the $ sign from? Where did you have to shine the laser on? When I did it on my Canadian $5 note I got something closer to the new £5 note.


  • #44999
    Profile photo of Andrew Normand

    Hi Alessio, I shone the laser through clear maple leaf is. The blue dot in the dollar below.
    Canadian security dollar

    The dollar I had is in the IOP Electromagnetic Workshop box and was a shown at the East Midlands day. I seem to remember that I could see no dollar pattern and was convinced that it is a true diffraction pattern. When I get hold of one again I will use my dino-light microscope to have a look. In the pictures above I used the dino-light to magnify the £5 pound note enough to see the little blobs of plastic.

    It is a definite security feature on the Canadian money and an interesting website is here.

    Where with the £5 note the diffraction pattern we see is just from the periodic structure of the plastic blobs

  • #45001
    Profile photo of Andrew Normand

    Thanks, someone shared this link in PTNC that shows how the new £5 notes work well to play an LP record 🙂 pretty cool too.

    • #45003
      Profile photo of Andrew Normand

      Somehow I don’t think my partner is going to be impressed if I try to use a fiver to play one of his treasured vinyls.

    • #45004
      Profile photo of Andrew Normand

      I just looked at a $20 note, the pattern in the dot looks like a very complicated maze, the type you get in puzzle books with right angled corners.

  • #48023
    Profile photo of Andrew Normand

    I did have a go at making a sound with the new 5 pound note. It did scratch the record a little


  • #48024
    Profile photo of Andrew Normand

    There is a good thread here on diffraction through a feather


  • #48397
    Profile photo of Andrew Normand

    Just got my first new 10 pound note. Still waiting to shine a laser through it.

    Shining UV on it is quite uneventful really

    crown 10 pound note

    I do like the new iridescence as a security feature.

    bank note 5

    My daughter pointed out how much how the crown looks like a face

  • #48404
    Profile photo of Andrew Normand

    It’s great that the BoE is celebrating diversity like that!

  • #49258
    Profile photo of Andrew Normand

    I have just come across a plastic Australian 5 dollar bank note. No interesting diffraction to report yet.

    The iridescence on the bird is amazing and I got from blue through green to red by rotating through an angle.

  • #49262
    Profile photo of Andrew Normand

    Nice one Dave,

    the Queen’s chin in the new £5 is quite interesting though. I often get students to find the spacing between the dots by measuring the diffraction pattern.

    lovely real application.

    • #49264
      Profile photo of Andrew Normand

      I’ve tried to get teachers interested in using diffraction to measure things, like the spacing on a DVD but they don’t appear to see the benefit (it isn’t in the curriculum)

      I bid on an interferometer on ebay once but was the under bidder. I think finding uses for these formulae helps to embed the principles and broaden the understanding.

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