Download De Broglie and Heisenberg

De Broglie's wavelength – and double slit experiment
The modern double-slit experiment is a demonstration that light and matter can display
characteristics of both classically defined waves and particles; moreover, it displays the
fundamentally probabilistic nature of quantum mechanical phenomena. A simpler form of the
double-slit experiment was performed originally by Thomas Young in 1801 (well before
quantum mechanics). He believed it demonstrated that the wave theory of light was correct
and his experiment is sometimes referred to as Young's experiment[1] or Young's slits. In 1924,
Louis-Victor de Broglie formulated the de Broglie hypothesis, claiming that all matter, not just
light, has a wave-like nature; he related wavelength (denoted as λ), and momentum (denoted as
p).
Double Slit. Unlike this typical interference experiment where plane waves fall on a double slit,
physicists have been able to observe the interference pattern from a wave packet consisting of
just two photons, measuring the effective wavelength in the process.
Heisenberg's uncertainty principle – single slit experiment
Heisenberg's uncertainty principle tells us that it is impossible to simultaneously measure the position
and momentum of a particle with infinite precision. In our everyday lives we virtually never come up
against this limit, hence why it seems peculiar. In a modern single slit experiment, a laser is shone
through a narrow slit onto a screen. As the slit is made narrower, the spot on the screen also becomes
narrower. But at a certain point, the spot starts becoming wider. This is because the photons of light have
been so localized at the slit that their horizontal momentum must become less well defined in order to
satisfy Heisenberg's uncertainty principle.