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WAVES INTERFERENCE YOUNGS DOUBLE SLIT EXPERIMENT |
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Interference
Youngs Double Slit Experiment Thomas
Young: English physician and scientist 1773 1829. He was a bright guy -
by age of 2 he could read fluently, by 4 he had read the bible twice and at
14 he knew eight languages. In 1801 Thomas Young, through his experiments provided
convincing evidence for the wave nature of light and was even able to measure
the wavelength for visible light.
Before this, the nature of light was not clear. Newtons view was that
light corresponded to a stream of particles. We now know that Newton was not
untirely wrong light has a dual nature, it behaves as a particle or a
wave. Young found that light directed through two
closely spaced pin holes recombines to produce fringes of brightness and
darkness on a screen. Young could explain this result as a wave interference
phenomenon. The light from each pin hole produces an interference pattern and
the light from the two separate pin holes also interfere. Bright spots are where the waves are in
phase and reinforce each other constructive interference. The waves are out
of phase at the positions of the dark fringes and cancel each other
destructive interference. The interference of light from two slits is
shown in figure 1. Notice, the interference pattern from the two slits is not the
superposition of the diffraction patterns from each slit.
Fig. 1. Interferecen from double slits. Figure 2 shows a computer stimulation for the interference of
red light from a pair of slits. Fig.2. Fig.2. Diffraction pattern for a two slit aperture. Predict Observe Explain Exercise Figure 2 gives the
default parameters for the double slit simulation. Predict the change in the
diffraction pattern, if one parameter was changed from the default values: Observe the
diffraction pattern to check your predictions and account for any
discrepancies.
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If you have any feedback, comments, suggestions or corrections
please email: Ian Cooper School of
Physics University of Sydney ian.cooper@sydney.edu.au Ian Cooper |