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Question
With the help of a neat labelled diagram, describe the Geiger- Marsden experiment
Solution
Geiger–Marsden experiment:
The setup of the Geiger–Marsden experiment is as shown below.
In this experiment, a narrow beam of α-particles from a radioactive source was incident on a gold foil. The scattered α-particles were detected by the detector fixed on a rotating stand. The detector used had a zinc sulphide screen and a microscope.
The α-particles produced scintillations on the screen which could be observed through a microscope. This entire setup is enclosed in an evacuated chamber.
They observed the number of α-particles as a function of scattering angle. Now, the scattering angle is the deviation (θ) of α-particles from its original direction.
They observed that most α-particles passed undeviated and only a few (~0.14%) scattered by more than 1°. Few were deflected slightly and only a few (1 in 8000) deflected by more than 90°. Some particles even bounced back with 180°.
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