Microscopes and Crystals - National High Magnetic Field Laboratory

ACTIVITY 16: USING MICROSCOPES TO INVESTIGATE BIREFRINGENCE
m6: Microscopes and Crystals
A CT
CTIVITY
Using Microscopes to Investigate
Birefringence in Crystals
In this activity you will be making crystals, observing some special properties of
crystals, and using microscopes with polarizers to observe birefringence in certain
crystals. Birefringence is another word for double refraction. When light passes
through a crystal that is birefringent, the light rays are bent or refracted twice.
In some materials a double image is produced. Double
refraction can be seen by comparing two materials, glass
and calcite. If a pencil mark is drawn on a piece of paper
and then covered with a piece of glass only one pencil
mark will be seen. However, if this same pencil mark is
covered with a piece of calcite crystal, and the crystal is
turned a certain way, then two pencil marks will be seen
rather than one.
Scientists use many tools to look at things like crystals. One of those tools is a
microscope. Although crystals are large compared to other things that
scientists look at using a microscope, there are many things we can learn by
observing crystals in different ways. You will look at the crystals that you
make using your eyes, your field microscope, and polarizers. Each time you
observe the crystals draw what you see.
MATERIALS:
! Field microscopes or other compound light microscopes
! Glass slides
! Epsom salt, copper sulfate, or vitamin C powder
! Warm water
! 2 Polarizers
! 1 Piece of calcite crystal
! Science Notebook
SCIENCE, OPTICS & YOU GUIDEBOOK
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