We started looking at half-life today. The attached file walks you through different types of half-life problem. There are some questions for you to try along they way. The answers are at the end, please don’t cheat!
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 sit in 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
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.
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.
Here are the answers to the waves & radiation questions.
I’ve put together a collection of exam questions from old standard grade and intermediate 2 papers that fit the national 5 curriculum. Try these before moving on to past papers and check your answers using the solutions that I will post next. No cheating!
I’ve attached a short guide to half-life calculations. There are some questions after each worked example, answers are at the end of the sheet.
I have attached revision notes from Scholar for the Electromagnetism unit. Your test will be after the Easter holidays.
You should be thinking about getting some of your project report finished so there is less to do when the deadline approaches. You can start writing up your underlying physics section and sort out the references you will include at the end of the report. I’ve attached a guide on referencing in the Vancouver style. Get back to me if you have any questions.
Thanks to Imperial College London for producing this booklet.
Here are the unit 2 study notes from Scholar that you asked for. Please do try logging in to Scholar and trying their interactive study materials.
Here is a link to some revision notes for the Our Dynamic Universe unit.
Here is the second set of revision notes for your test.