Rutherford Experiment

Ruther Ford Alpha Scattering Experiment : 

Ruther Ford Alpha Scattering Experiment Made by: Harshit Gupta Romi S Chandra Class:12 `A’

History of Rutherford Experiment : 

History of Rutherford Experiment In Ernest Rutherford's laboratory, Hans Geiger and Ernest Marsden (a 20 yr old undergraduate student) carried out experiments to study the scattering of alpha particles by thin metal foils. In 1909 they observed that alpha particles from radioactive decays occasionally scatter at angles greater than 90°, which is physically impossible unless they are This led Rutherford to deduce that the positive charge in an atom is concentrated into a small compact nucleus. During the period 1911-1913 in a table-top apparatus, they bombarded the foils with high energy alpha particles and observed the number of scattered alpha particles as a function of angle. Based on the Thomson Model of the atom, all of the alpha particles should have been found within a small fraction of a degree from the beam, but found a few scattered alphas at angles over 140 degrees from the beam. Rutherford's remark "It was quite the most incredible event that ever happened to me in my life. It was almost as incredible as if you had fired a 15-inch shell at a piece of tissue paper and it came back and hit you." The scattering data was consistent with a small positive nucleus which repelled the incoming positively charged alpha particles. Rutherford worked out a detailed formula for the scattering which matched the to high precision. The source used in the Rutherford experiments was purified radium contained in a thin-walled 1-mm diameter glass tube. The source strength was about 0.1 curie or about 4 billion nuclear decays per second. The alpha particles were allowed to pass through a small diaphragm and were directed toward a thin foil target. The detector was a small (10-6 m2) zinc sulfide screen mounted a few centimeters away from the target. (Rolfe) scattering off something more massive than themselves.

Model of Experiment : 

Model of Experiment

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In the early days of atomic theory, many physicists tried to explain the model of an atom. In 1902, Ernest Rutherford showed that alpha particles emitted from the decay of unstable radioactive materials were electrically charged helium nuclei travelling at high speed. In 1909, Rutherford used alpha particles to investigate the composition of gold foil (i.e. to explain the model of an atom). IN THE BEGINNING……

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To investigate the composition of gold foil using alpha particles (i.e. to explain the model of an atom). Aim

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Apparatus Rutherford’s alpha scattering apparatus:

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Procedure Rutherford fired alpha particles through a piece of gold foil and used a zinc sulphide detector to detect the scattered alpha particles and their location. Formula for experiment are:

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Radioactivity Radioactivity refers to the particles which are emitted from nuclei as a result of nuclear instability. Because the nucleus experiences the intense conflict between the two strongest forces in nature, it should not be surprising that there are many nuclear isotopes which are unstable and emit some kind of radiation. The most common types of radiation are called alpha ,beta and gamma radiation, but there are several other varieties of radioactive decay Radioactive decay rates are normally stated in terms of their half-lives and the half-life of a given nuclear species is related to its radiation risk. The different types of radioactivity lead to different decay paths which transmute the nuclei into other chemical elements. Examining the amounts of the decay products makes possible radioactive Dating. Radiation from nuclear sources is distributed equally in all directions, obeying the inverse square law.

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Rutherford’s experiment found that: Most of the alpha particles passed through the gold foil undeviated. A few alpha particles were deflected from their path but continued through the gold foil. A small number of alpha particles rebounded. Results

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As most alpha particles passed through the gold foil atoms undeviated, Rutherford concluded that most of the atom was actually empty space. From the results of his experiment, Rutherford explained: The deviation of some alpha particles from their original path were due to positive charges within the foil. Conclusion

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From the results of his experiment, Rutherford explained: Conclusion A small number of alpha particles had rebounded because they collided with something much larger and heavier and which contains a concentrated region of positive charge.

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As a result of his observations, Rutherford suggested that the atom had a positively charged centre which contained most of the mass. He called the heavy positively charged centre the nucleus. He went on to suggest that the nucleus was surrounded by orbiting electrons required for electrical neutrality. Conclusion

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As a result of his observations, Rutherford suggested that the atom had a positively charged centre which contained most of the mass. He called the heavy positively charged centre the nucleus. He went on to suggest that the nucleus was surrounded by orbiting electrons required for electrical neutrality. Conclusion

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As a result of his observations, Rutherford suggested that the atom had a positively charged centre which contained most of the mass. He called the heavy positively charged centre the nucleus. He went on to suggest that the nucleus was surrounded by orbiting electrons required for electrical neutrality. Conclusion

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As a result of his observations, Rutherford suggested that the atom had a positively charged centre which contained most of the mass. He called the heavy positively charged centre the nucleus. He went on to suggest that the nucleus was surrounded by orbiting electrons required for electrical neutrality. Conclusion

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As a result of his observations, Rutherford suggested that the atom had a positively charged centre which contained most of the mass. He called the heavy positively charged centre the nucleus. He went on to suggest that the nucleus was surrounded by orbiting electrons required for electrical neutrality. Conclusion

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Alpha Radioactivity Alpha particle emission is modeled as a barrier penetration process. The alpha particle is the nucleus of the helium atom and is the nucleus of highest stability.

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Alpha Binding Energy The nuclear binding energy of the alpha particle is extremely high, 28.3 MeV. It is an exceptionally stable collection of nucleons, and those heavier nuclei which can be viewed as collections of alpha particles (carbon-12, oxygen-16, etc.) are also exceptionally stable. This contrasts with a binding energy of only 8 MeV for helium-3, which forms an intermediate step in the proton proton fusion cycle

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Alpha, Beta, and Gamma Historically, the products of radioactivity were called alpha, beta, and gamma when it was found that they could be analyzed into three distinct species by either a magnetic field or an electric field.

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Regardless of the nature of the force in an elastic collision, to get a scattering angle greater than 90 degrees, the target must be more massive than the projectile. Conditions for large angle scattering

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Modern measurements show that the average nucleus has a radius in the order of 10-15 m. This is 100, 000 times smaller than the radius of a typical atom. Observations we observe that three rays are emitted from radioactive elements. They are alpha, beta and gamma in which alpha is positive ray beta is negative ray and gamma is neutral.