Chapter: 11th 12th std standard Class Physics sciense Higher secondary school College Notes
Laue experiment
Laue experiment
Von Laue, in 1913, suggested that a crystal can
act as a three dimensional grating for an X-ray beam. The experimental
arrangement used to produce diffraction in X-rays by Laue is shown in Fig (a).
X-rays from the X-ray tube is collimated into a fine beam by two slits S1
and S2. The beam is now allowed to pass through a zinc sulphide (ZnS) crystal. The emergent rays are made
to fall on a photographic plate P. The diffraction patten so obtained consists
of a central spot at O and a series of spots arranged in a definite pattern
about O as shown in Fig 6.17b. The central spot is due to the direct beam,
whereas the regularly arranged spots are due to the diffraction pattern from
the atoms of the various crystal planes. These spots are known as Laue spots.
The Laue experiment has established following two important facts :
(i) X-rays are electro magnetic waves of extremely short wave length.
(ii) The atoms in a crystal are arranged in a regular three dimensional lattice.
X-rays
A German scientist, Wilhelm Roentgen, in 1895,
discovered X-rays when he was studying the phenomenon of discharge of
electricity through gases.
After performing a series of experiments,
Roentgen concluded that when a beam of fast moving electrons strike a solid
target, an invisible penetrating radiation is produced. Due to the unknown
nature of the radiation, Roentgen called these radiations as X - rays.
X-rays are electromagnetic waves of short
wavelength in the range of 0.5 Å to 10 Å. Roentgen was awarded Nobel prize in
1901 for the discovery of X-rays.
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