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While trying to make somewhat of a timeline of the history of ionizatig radiation, i am wondering about the following questions:

The first photoelectrical effect was found 1839 by Alexandre Becquerell - the photoelectrical effect and therefore UV-light, would be the first ionization radiation. Is that right?

While i am quite sure about it for electromagnetical radiation, i am not sure about particle radiation. Was there any ionizating particle radiation before the discovery of uran-radiation by Antoine Becquerell?

A source for proof would be quite a nice extra, thanks!

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X-rays were discovered in 1895, a year before Becquerel discovered Uranium's radiation (1896). And, while it is not ionising, Hertz worked on radio waves as early as 1886, following theoretical work by Maxwell in 1861.

Here are some links: A list of the discovery dates of particles (or rays, before they were considered particles):

Discovery of uranium radiation:

Heinrich Hertz:


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thanks, your link to the timeline made me remember the timeline of the atomic-model, so particle-radiation is out of the question. However, what is now the correct answer? UV-Light is ionising, with the right materials even visible light is; so would it be 1839 by becquerel, 1886 by hertz or 1895 by Schumann, who had discovert VUV-light that is even by today german standards categorized as ionising? I am not convinced, that it should be X-Rays. – Jook Mar 7 '13 at 14:06
There is no firm boundary between ionising and non-ionising radiation. One definition of ionising radiation is that it must have an energy of at least 10 eV per particle. That implies a wavelength of 125 nm, well into the UV. I do not know who first measured radiation at this short wavelength, but it may have been after X-rays were discovered. – hdhondt Mar 9 '13 at 11:02

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