1 Rutherford’s Gold foil scattering experiment Introduction: In physics, Rutherford scattering is a phenomenon that was explained by Ernest Rutherford in 1909, and led to the development of the Rutherford model (planetary model) of the atom, and eventually to the Bohr model. The initial discovery was made by Hans Geiger and Ernest Marsden in 1909 when they performed the gold foil experiment under the direction of Rutherford, in which they fired a beam of alpha particles (helium nuclei) at layers of gold leafs only a few atoms thick. The intriguing result showed that around 1 in 8000 alpha particles were deflected by very large angles (over 90°), while the rest passed straight through with little or no deflection. From this, Rutherford concluded that the majority of the mass was concentrated in a minute, positively charged region (the nucleus) surrounded by electrons. When a (positive) alpha particle approached sufficiently close to the nucleus, it was repelled strongly enough to rebound at high angles. The small size of the nucleus explained the small number of alpha particles that were repelled in this way. Schematic of the Rutherford scattering is shown above. Most particles travel straight through the gold foil but about 1 in 8000 was turned through a large angle. Principle: The relationship between the angle of scattering and the rate of scattering of - particles by gold foil is examined with a semiconductor detector. This detector has high detection probability for observing -particles so that the number of pulses agrees exactly with the number of -particles striking the detector. Alpha source very few some Many particles gold foil
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Rutherford’s Gold foil scattering experiment
Introduction:
In physics, Rutherford scattering is a phenomenon that was explained by Ernest
Rutherford in 1909, and led to the development of the Rutherford model (planetary model) of the
atom, and eventually to the Bohr model. The initial discovery was made by Hans Geiger and
Ernest Marsden in 1909 when they performed the gold foil experiment under the direction of
Rutherford, in which they fired a beam of alpha particles (helium nuclei) at layers of gold leafs
only a few atoms thick. The intriguing result showed that around 1 in 8000 alpha particles were
deflected by very large angles (over 90°),
while the rest passed straight through with
little or no deflection. From this,
Rutherford concluded that the majority of
the mass was concentrated in a minute,
positively charged region (the nucleus)
surrounded by electrons. When a (positive)
alpha particle approached sufficiently
close to the nucleus, it was repelled strongly enough to rebound at high angles. The small size of
the nucleus explained the small number of alpha particles that were repelled in this way.
Schematic of the Rutherford scattering is shown above. Most particles travel straight through
the gold foil but about 1 in 8000 was turned through a large angle.
Principle: The relationship between the angle of scattering and the rate of scattering of -
particles by gold foil is examined with a semiconductor detector. This detector has high detection
probability for observing -particles so that the number of pulses agrees exactly with the number
of -particles striking the detector.
Alpha source
very few
some
Many particles
gold foil
2
Objective:
1. The particle rates are measured at different angles of scattering between about 20 - 90 degrees.
The measurements are compared with the particle rates calculated by means of the Rutherford
theory for the measurement geometry used.
2. The particle rates are measured in the case of scattering by Aluminum and Gold with identical
angles of scattering in each case. The ratio of the two particle rates is compared with the particle
rate calculated from Rutherford’s scattering equation.
Equipments:
Annular diaphragm w. gold and aluminum foil U-magnet, large