Welcome to the Hooke College of Applied Science's course on Polarized Light Microscopy.
If you were to see an image like this under the microscope, would you be able to identify
it?
It looks like a shard of glass, doesn't it?
But what if I told you that by changing the configuration of just one component on the
polarizing light microscope, that I could conclude that this is not glass, but rather,
was consistent with quartz?
Over the next several modules included in this course, I'd like to teach you how to
identify materials based on their optical characteristics, using the polarizing light
microscope.
My name is Tom Van Howe, and I've been an instructor at Hooke College of Applied Sciences
for over a decade.
I've taught literally thousands of students how to use the polarizing light microscope
to identify materials.
When not teaching, I'm a research microscopist in the Light MIcroscopy department of McCrone
Associates where I routinely use a polarizing light microscope similar to that which we
will be using in this course to view, characterize, image, and identify unknown materials and
foreign matter particulate.
Although I've worked in the field of microscopy and microbiology for nearly three decades,
I thoroughly enjoy the field of investigative microscopy and the problem-solving experience
which comes with it, and I am truly most passionate about sharing with students, like yourself,
what I know about microscopy.
In this polarized light microscopy course, we will be covering the following topics:
the polarizing light microscope components and their functions; microscope alignment,
ocular scale calibration, microscope qualification, and routine maintenance; a basic understanding
of light, optics, and light microscopy; a brief introduction to optical crystallography;
ordinary light observations, such as particle size, morphology, and transmitted color; plane
polarized light observations, such as refractive indices and pleochroism; observations in crossed
polarized light, including isotropy, birefringence, sign of elongation, extinction characteristics,
and interference figures with optic sign.
And lastly, how all these optical characteristics relate to one another and aid us in the identification
of the materal.
Each of these sections will be broken down into their own learning modules, and can be
paused or played back at any time for review.
Each module lasts for approximately 30-90 minutes.
Some section will take you a little longer if you participate in the laboratory exercises.
It may be beneficial to be near a polarizing light microscope while watching this course,
so that you can participate along with the exercises.
It is recommended that you go through the modules in order, as each of the sections
will build upon previously-learned material.
Also, please keep in mind that this course is intended to be introductory in nature,
to the polarizing light microscope.
Although it may not cover more advanced techniques, it should give you a good foundation for learning.
Equipment that you should have available while learning includes the following: a polarizing
light microscope; sample specimens; a certified stage micrometer; an orientation plate; a
sodium D filter; Michel Levy Chart; and if you're like me, and bad at math, a calculator.
In this course, we will be using primarily an Olympus BX-51 polarizing light microscope.
However, it is our intent that the instructions will be general enough to be used with any
well-equipped polarizing light microscope.
Throughout this course, I'll also be using prepared slides; if you do not have prepared
slides, several sets of slides are commercially available from suppliers of microscope supplies.
If you do not have these available to you, or they are not within your budget, when possible,
I'll be using, as exemplars, common materials which are commercially available to most users.
These include: table salt, sucrose, monosodium glutamate, talcum powder, baking soda, corn
starch, container glass, quartz, calcium carbonate, human hair, cotton fibers, acetate fibers,
acrylic fibers, nylon fibers, and colorless polyester fibers.
In regards to mounting media, many of the slides which I'll be using as examples are
mounted in a permanent media called "Meltmount" which has a refractive index of 1.66.
If you do not have prepared slides, it is best, at minimum, to have deionized water
available, but keep in mind that this may cause some of your materials to dissolve.
And other refractive index liquids, including 1.552, 1.54, 1.56, and 1.66 would be ideal
for practice, but are not necessary to learn the concepts.
Lastly, as a companion tool, I highly recommend a copy of Essentials of Polarized Light MIcroscopy
by John Gustav Delly, which is published by Hooke College of Applied Sciences.
Although there are several great references on the subject of polarized light microscopy,
I find this book to be the most complete and user-friendly, from an initial learning perspective.
It expounds on many of the topics taught in this course, and will reaffirm the concepts
you've learned.
It is our hope that you will find this course useful and effective as a learning tool, as
well as an inspiration for whatever your career or hobby may be.
Before we fully immerse ourselves in polarized light microscopy, let's first get a basic
understanding of what a microscope is, and how it can help us characterize, and possible
identify, materials.