X-rays are a form of electromagnetic radiation. They have a much higher frequency than visible light or ultraviolet. The diagram below, taken from Wikipedia, shows where x-rays fit into the electromagnetic spectrum.
image by Materialscientist
Wilhelm Röntgen discovered x-rays and the image below is the first x-ray image ever taken. It shows Mrs. Röntgen’s hand and wedding ring. The x-ray source used by Röntgen was quite weak, so his wife had to hold her hand still for about 15 minutes to expose the film. Can you imagine waiting that long nowadays?
This was the first time anyone had seen inside a human body without cutting it open. Poor Mrs. Röntgen was so alarmed by the sight of the image made by her husband that she cried out “I have seen my death!” Or, since she was in Germany, it might have been
“Ich habe meinen Tod gesehen!“
that she actually said.
Röntgen continued to work on x-rays until he was able to produce better images. The x-ray below was taken about a year after the first x-ray and you can see the improvements in quality.
Notice that these early x-rays are the opposite of what we would expect to see today. They show dark bones on a lighter background while we are used to seeing white bones on a dark background, such as the x-ray shown below. The difference is due to the processing the film has received after being exposed to x-rays.
In hospitals, x-rays expose a film which is then developed and viewed with bright light. X-rays are able to travel through soft body tissue and the film behind receives a large exposure. The x-rays darken the film. More dense structures such as bone, metal fillings in teeth, artificial hip/knee joints, etc. block the path of x-rays and prevent them from reaching the film. Unexposed regions of the film remain light in colour.
Röntgen’s x-ray films would have involved additional processing steps. The exposed films were developed and used to create a positive. In creating a positive, light areas become dark and dark areas become light. So the light and dark areas in Röntgen’s x-rays are the opposite of what we see today. Our modern method makes it easier to detect issues in the bones as they are the lighter areas.
Röntgen was awarded the first ever Nobel Prize for Physics in 1901 for his pioneering work in this field of physics.
Medical imaging has come a long way since Röntgen’s discovery of x-rays. This promotional video from German company Siemens outlines the advances that have been made since the early 20th century.
I have attached a recording of a short BBC radio programme about the first x-ray and what people in the Victorian era thought of these new images. Click on the player at the end of this post or listen to it in iTunes.
There is a range of material available, including examples of candidate evidence with commentaries, as part of our Understanding Standards programme. This material is for teachers and lecturers to help them develop their understanding of the standards required for assessment. As new material is developed we will publish this information in our weekly Centre News. All material available can be found in the following locations:
- Available from our Understanding Standards website Material relating to externally assessed components of course assessment, with the exception of those subject to visiting assessment.
Available from our secure website Material relating to internally assessed components of course assessment, and components of course assessment which are subject to visiting assessment. In addition, material relating to freestanding units which are no longer part of National 5 courses can be found on this website. Teachers and lecturers can arrange access to these materials through their SQA Co-ordinator.
More information on Understanding Standards material for this subject can be found on our Understanding Standards website at http://www.understandingstandards.org.uk/Subjects/Physics.
The National 5 webinar provides a detailed overview of the revised course assessment for this subject.
National 5 Physics 20 June 2017
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