３．History of radiation

Dr.Bcquerel／Mr. And Mrs. Curie／Rutherford

Radiation and radioactivity were discovered 100years ago. In fact, it is recent event.

In 1896, Antoine Becquerel studied X-ray. In those days, X-ray is the first radiation discovered by Wilhelm Rontgen. But, radioactive material and radioactivity wasn’t found.
He must have emitted light to sample including uranium for study but he couldn’t do because the cloudy weather was holding. He tried examining the sample and he discovered anther radiation not X-ray. As result, he found that radiation was in proportion to uranium density.
That’s how radioactivity and radioactive material is discovered.

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In 1898, Marie Curie discovered thorium with her husband, Pierre Curie by observing ionization of radiation. Forecasting that uranium ore includes other radioactive material without uranium, they discovered polonium and radium.
Discovery of radium gathered attention of many scientists. Radium has wonderful properties because it has a strong radioactivity. For example, it shines blue and so on.
According to, that radium continued to emit energy surprised people. It seemed that radium would be emitting energy forever because its half-life is around 1602years.

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Present, we know structure of an atom. This is because of research of radioactivity.

In 1902, Ernest Rutherford put forward the hypothesis that radiation is emitted when an atom collapses to change into another atom. That amazed people. Because atom is regarded as unchanging thing then.
In 1905, he proposed that alpha-ray’s true character is an atomic nucleus of helium.
In 1911, he put forward atomic structure which we believe in now.
He rendered remarkable services, discovery of alpha-ray and beta-ray and prophecy of existing a neutron.

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Ernest Rutherford（1871～1937）

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