Leaving Cert Physics The Atom & Radioactivity: Read the following passage and a

Question

Read the following passage and answer the accompanying questions.

Ernest Rutherford (1871–1937, Nobel Prize 1908) was a brilliant student from New Zealand who, thanks to a grant, moved to the glorious Cavendish Laboratory in Cambridge, full of hopes and ambitions. Later in his life he became a physics professor at the University of Manchester.

One day in 1909, in Manchester, he suggested to his collaborator Hans Geiger and to his student Ernest Marsden that they study the deflection of the so-called alpha-particles. These are positively charged helium ions produced by a radioactive source of radium bromide. This definition shows what the alpha-particles are. Experiments of this kind had already been performed, and it had been observed that the alpha-particles are only slightly deflected when they cross the film.

The novelty of Rutherford’s suggestion was that he asked his collaborators to check if any alpha-particle bounced back instead of going through the film. Why should a thin metal film reflect heavy high-speed bullets, like the alpha-particles produced by a radioactive source? Geiger and Marsden indeed observed that some alpha-particles were bouncing back.

In Rutherford’s words: “It was quite the most incredible event that has ever happened to me in my life”. He had not expected such a huge deflection from what physicists assumed were positively charged particles, and they had observed that some alpha-particles were bouncing back.

The result is a cloud of light electrons, carrying all the negative charge.

(Adapted from A Zeptospace Odyssey, Gian Francesco Giudice, Oxford University Press, 2010)

Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question 11 - 2015

Worked Solution & Example Answer:Read the following passage and answer the accompanying questions - Leaving Cert Physics - Question 11 - 2015

What are alpha-particles?

Name a source of alpha-particles.

What material was used as the target in the experiment?

How did Geiger and Marsden detect the alpha-particles?

What was the surprising result they observed?

How was alpha-particles were deflected in the alpha-particle experiment?

Outline what the Geiger-Marsden experiment revealed about the structure of the atom.

For what invention is Hans Geiger most famous?

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