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3.1 Radioactivity and its history

3.1 Radioactivity and its history. (Sec 10.1 pg 275-279). Starting in the late 1800s, there was a lot of scientific study into radioactivity in a short period of time, and it involved the work of many scientists (Fig.1 p.275). .

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3.1 Radioactivity and its history

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  1. 3.1 Radioactivity and its history (Sec 10.1 pg 275-279)

  2. Starting in the late 1800s, there was a lot of scientific study into radioactivity in a short period of time, and it involved the work of many scientists (Fig.1 p.275).

  3. The first major discovery was made in the 1870s using something called a cathode ray tube (old fashioned TVs and computer monitors – see Fig.2 p.276). • They found that a beam of particles came off of a negative electrode (cathode) and travelled to a positive electrode (anode). • These particles were found to carry a negative charge, and were later were named electrons by J.J. Thompson.

  4. In 1895 Wilhelm Röntgen produced X-rays by bouncing a beam of electrons off a sheet of metal (Fig.4, p.276) – he noticed the emitted rays caused fluorescent minerals to glow, and also exposed photographic film. • He named them ‘X-rays’ because he had no idea what they were. • He discovered X-rays could penetrate some things like paper and skin, but not materials like metal and bone (Fig.5 p.277).

  5. While Röntgen was experimenting with X-rays Henri Becquerel was experimenting with fluorescent (glowing) materials. • He thought they might give off X-rays so he tried exposing them to film, and it worked. He thought the X-rays were absorbed by the rocks from the Sun.

  6. He tried the experiment on a cloudy day and found that it still worked. This meant the rays were being emitted from the rocks themselves. • He also noticed these rays were deflected by a magnet, demonstrating they were not X-rays. • He named this new ray after himself – for a time they were called ‘Becquerel rays’ CLIP: http://science.howstuffworks.com/29296-100-greatest-discoveries-radioactivity-video.htm

  7. Marie Curie and her husband then experimented with Uranium, polonium, etc and found this radiation was unaffected by temperature, pressure and any other physical factor. • They eventually concluded that the radiation came from the core of the atom, and called this spontaneous emission of radiation radioactivity.

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