3B Scientific Demonstration Polariscope - Manual

3B SCIENTIFIC ® PHYSICS
1
Demonstration Polariscope U8472580
Instruction Sheet
06/08 ALF
1 Top plate with analyser
2 Specimen clamp
3 Base plate with polariser
4 Clips for applying tension
5 Specimens
1. Description
The demonstration polariscope is used in
combination with an overhead projector to visually
demonstrate the stress distribution in specimens
under tension or compression.
The polariser is contained in the base plate of the
instrument and the analyser is in the rotatable top
plate. A tensile or compressive load can be applied to
the specimen by means of a screw mechanism. When
the specimen is viewed in polarised light the
resulting mechanical stresses become visible as
coloured fringes.
The mechanical stresses cause the specimen to
become bi-refringent (doubly refracting), so that the
incident polarised light is split into two components
vibrating at 90
o to each other. Their phase velocities
differ by an amount that increases in proportion to
the stresses in the specimen. The incident light is
elliptically polarised, and consequently it cannot be
completely filtered out by the analyser. The
birefringence depends strongly on the light
wavelength. Consequently, if white light is used, the
system of fringes consists of light modified such that
the colours are mixtures of those components of the
spectrum that are not eliminated. Fringes of a
specific colour indicate positions of equal stress.
2. Equipment supplied
1 Basic instrument
2 Metal clips for applying tension
1 Ring, 60 mm diam.
× 10 mm thickness
1 Rectangular block, 60
Ч 10 Ч 10 mm 3
2 Rectangular blocks, 20
Ч 10 Ч 10 mm 3
3 Equilateral triangular blocks 17
× 10 mm 2
3. Technical data
Specimens: Epoxy resin
Instrument dimensions: 150
Ч15Ч45 mm 3 approx.
Total weight: 820 g approx.
4. Operation
Additional equipment needed:
1 Overhead projector (230 V, 50/60 Hz) U30150-230
or
1 Overhead projector (115 V, 50/60 Hz) U30150-115
• Place the polariscope on the overhead projector.