I’ve come across three completely separate references to the early days of X-rays recently that have intrigued me. X-rays are now on the HL 2014 syllabus (for first exams in May 2016) under both topic 21 and Option A.  When teaching Topic 2: Atomic structure it is certainly also worth including the work of Henry Moseley who used X-rays to show that each element is defined by a unique atomic number.

It is a well-known fact that X-rays were discovered by Wilhelm Roentgen in 1895. Roentgen was a professor of Physics in Bavaria who was exploring the path of electrical rays in a partially evacuated glass tube when he realised that rays were given off that could penetrate a number of objects. He used his own hand, and later that of his wife, to take the first X-rays of the internal structure of the body.

I was therefore surprised to find a plaque (see above) in my local hospital in Bridgend, South Wales honouring what appeared to be the discovery of X-rays as long ago as 1785. This plaque commemorates Dr William Morgan (1750–1833) and states that he constructed the first X-ray tube. This would tend to suggest that he actually discovered X-rays but the TOK part of me says that if you read it carefully he just constructed a tube that produced X-rays not that he recognised that they were present. 

In an article published today in Radiology, Gerrit Kemerinck of Maastricht University in Holland has compared an X-ray machine made in 1886 with a modern machine. The old machine in Maastricht was assembled originally by a High School teacher called  H.J. Hoffmans together with the director of the local hospital only a few months after Roentgen announced his discovery. This machine, which has lain in a warehouse for many years, still functions well but to obtain a comparable image to a modern machine radiation some ten times higher is needed and the image, although recognisable, is not as sharp. 

This leads on to the third reference I came across. In the workshop I was running for experienced IB Chemistry teachers recently in Berlin one of the participants talked about using X-rays in the 1920s to determine how well shoes fitted. I can remember these machines well myself as their use continued into the 1960s. It used to be great fun as a kid to put your foot into one of these 'pedoscopes' (see right) and see all the bones in your feet. Parent would stress how useful these machines were as having properly fitting shoes would ensure that their children’s feet were less likely to suffer problems in the future. It is a good example of how people use 'current' scientific knowledge with the very best of intentions without realising the possible potential for damage. Later, of course, the machines were banned when it was realised the harm that repeated exposure to X-rays can cause.