Microscope Shopping List

Saturday July 31, 2010

This lab is an introduction to the microscope. We’re going to cover how to use a compound microscope, the basics of optics, slide preparation, and why we can see things that are invisible to the naked eye.



What’s a compound microscope? Compound microscopes are basically two lenses put together to make things appear larger. If you’ve ever used magnifying glass, you’ve noticed how the lens makes words easier to read. If you were to look through two magnifiers (one stacked on top of the other with space in between), you’ve seen this effect multiply to create an even larger image. That’s exactly what a compound microscope does. It uses stacked lenses to greatly increase the magnification.


I’ll show you how to get the most out of your investment by learning how to operate a microscope and prepare specimen slides. Click here for a printer-friendly version of this page.


Selecting a Microscope

The first thing you need to do is select a compound microscope. Cheap microscopes are going to frustrate you beyond belief, so we’ve provided recommendations that will get last your kids through college.


It can be a daunting task to find high quality microscopes and accessories at affordable prices. Here are a couple of recommendations for microscope and equipment that will last your kids through college. You’ll also need additional items like slides, coverslips, tweezers, and other basic equipment.

The microscope you select will last a long time. Expect to pay at least $100 for a decent microscope that will provide many years of use. Here are ones we recommend investing in…


Economy Model: The Kids Microscope is a great entry level microscope for under $110. It meets the optical requirements to do our microscope labs but has only single intermediate focusing. It is also available in a cordless LED model that you can use in the field. If your children are young, this may be a good scope to start out with.
Student Model: The Home Microscope is an excellent 5th – 12th grade level microscope with fluorescent lighting that will really meet all the microscope needs of most families. It is well built with very good optics and will stand up to many years of use. I recommend the additional mechanical stage, as stage clips can be frustrating when working at high power!
Advanced Model: There is a Serious Student Model that includes the mechanical stage, iris diaphragm for lighting control, extra 100x oil immersion objective for 1,000x magnification, and immersion oil. This one will take you far in your studies of the micro world. Using the 100x objective with immersion oil is more challenging but also very rewarding as your child is able to see more and develop advanced microscope skills.
All-the-Bells-and-Whistles Model: The Ultimate Home Microscope is really a great microscope (and very similar to the one I personally use with the teaching head attached). This is a university/lab level microscope that is built to withstand the rigors of daily use. This scope is heavier, sturdier, and has all the advanced features like 100x oil immersion objective, iris diaphragm lighting control and a mechanical stage with very easy to use controls. It is also available in a binocular model that is more comfortable to use.When your microscope arrives, keep it in its packaging until you watch the next video. I’ll show you how to handle it, store it, and where not to touch.
No matter which microscope you select, you’ll want to be sure it meets these criteria: at least three objectives (40X, 100X, 400X) and the optics are all glass to provide better quality images and the microscope frame construction is metal to provide the durability you want. Most microscopes include a dust cover and custom fit styrofoam box for safe storage. Optional additions include a mechanical stage (which we highly recommend), a fourth 100x objective lens (for 1,000x magnification), and adjustable iris diaphragm for better lighting/contrast control.
By the way, if you’re considering the the fourth 100x lens, make sure you get the special “oil immersion” objective. Light tends to do weird things when you magnify it that much, and to avoid these kinds of problems, scientists use a drop of oil on the slide to connect the objective with the slide. However, you can’t do this trick with just any objective lens – you need to have a special kind of lens that won’t get mussed up when contacted with oil (hence the “oil immersion” type).

Where to Find Other Essentials

In addition to a microscope, you’ll also need additional items like slides, cover slips, tweezers, and other basic equipment. Here’s what you need to complete the labs in this section:



Supplemental Equipment:

These items are not required for this lab, however if your budget allows for these items in the future, they are very nice to have…

Prepared Slide Sets: Using our labs you will learn to make different kinds of microscope slide mounts and examine a variety of samples that you can easily collect. Prepared slides contain specimens that have been professionally stained and prepared so that you can expand your microscope studies to a great variety of plant and animal life that you would otherwise not have access to. The general slide set and the biology slide set are two sets that contain a great variety of specimens to expand your microscopic studies.
Microscope Case: While the dust cover and styrofoam box that come with your microscope provide a good degree of protection, you may want to consider a microscope case to provide greater protection and convenience in carrying and storing your microscope. These cases have the added advantage of also storing your microscope accessories with your microscope in one location.
Digital Microscope: This one is actually cheaper than most optical models listed above, and I’ve used it when teaching kids. The best part is, all kids can view at the same time, and you can take both pictures and video of your specimens while viewing. It’s really a great deal for the price. The one I really like is the Celestron 44340 LCD.

Can’t afford a microscope?

I’ll show you how to build a very simple microscope using two handheld magnifying lenses! All you need is an afternoon, a few kids, and two magnifiers per kid. Now it doesn’t come close to any of the microscopes above, but it will allow you to do some basic experimentation. (The magnifiers do not need to be the same magnification.) Gather up a few coins, dead bugs, and plant specimens and you’ll be all set for a microscope adventure.


Microwhat?

Saturday July 31, 2010

Welcome to our unit on microscopes! We’re going to learn how to use our microscope to make things appear larger so we can study them more easily. Think about all the things that are too small to study just with your naked eyeballs: how many can you name?


Let’s start from the inside out – before you haul out your own microscope, we’re going to have a look at what it can do. I’ve already prepared a set of slides for you below.  Take out a sheet of paper and jot down your guesses – here’s how you do it:


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Anatomy of the Microscope

Saturday July 31, 2010

Nose? Objective? Stage? What kind of class is this?  Well, some of the names may sound a bit odd, but this video will show you what they are and how they are used. As you watch the video, touch the corresponding part of your microscope to get a feel for how it works.


NOTE: Be very careful NOT to raise the stage too high or you’ll crack the objective lens!  Always leave a space between the stage and the lens!! Anytime you use the coarse adjustment knob, always look at the stage itself, NOT through the eyepiece (for this very reason). When you use the fine adjustment knob, that’s when you look through the eyepiece.




More questions to ask:

1. After you’ve learned the different parts of the microscope, swing around and teach it to a nearby grown-up to test your knowledge. See if you can find all these parts: eyepiece, base (legs), objective lens, eyepiece, diaphragm (or iris), stage, fine and coarse adjustment knobs, mirror/lamp, nose.


2. Show your grown-up which parts never to touch with your fingers.


3. What’s the proper way to use the coarse adjustment knob so you don’t crack the objective lens?


Care and Cleaning

1. Pick up the microscope with two hands. Always grab the arm with one hand and the legs (base) with the other.


2. Don’t touch the lenses with your fingers. The oil on your fingers will smudge and etch the lenses. Use an optical wipe if you must clean the lenses. Steer clear of toilet paper and paper towels – they will scratch your lenses.


3. When you’re done with your scope for the day, reset it so that it’s on the lowest power of magnification and lower the stage to the lowest position. Cover it with your dust cover or place it in its case.


Preparing a Dry Mount Slide

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope activity before you start here!


This is simplest form of slide preparation!  All  you need to do is place it on the slide, use a coverslip (and you don’t even have to do that if it’s too bumpy), and take a look through the eyepiece.  No water, stains, or glue required.


You know that this is the mount type you need when your specimen doesn’t require water to live. Good examples of things you can try are cloth fibers (the image here is of cotton thread at 40X magnification), wool, human hair, salt, and sugar. It’s especially fun to mix up salt and sugar first, and then look at it under the scope to see if you can tell the difference.


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Preparing a Wet Mount Slide

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope activity before you start here!


Anytime you have a specimen that needs water to live, you’ll need to prepare a wet mount slide. This is especially useful for looking at pond water (or scum), plants, protists (single-cell animals), mold, etc. When you keep your specimen alive in their environment, you not only get to observe it, but also how it eats, lives, breathes, and interacts in its environment.


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Slide Preparation: Staining

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope and also the Wet Mount activities before you start here!


If your critter is hard to see, you can use a dye to bring out the cell structure and make it easier to view.  There are lots of different types of stains, depending on what you’re looking at.


The procedure is simple, although kids will probably stain not only their specimens, but the table and their fingers, too.  Protect your surfaces with a plastic tablecloth and use gloves if you want to.


We’re going to use an iodine stain, which is used in chemistry as an indicator (it turns dark blue) for starch. This makes iodine a good choice when looking at plants. You can also use Lugol’s Stain, which also reacts with starch and will turn your specimen black to make the cell nuclei visible. Methylene blue is a good choice for looking at animal cells, blood, and tissues.


In addition to your specimen, you’ll need to get out your slides, microscope, cover slips, eye dropper, tweezers, iodine (you can use regular, non-clear iodine from the drug store), and a scrap of onion. If you can find an elodea leaf, add it to your pile (check with your local garden store). Here’s what you do:


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Slide Preparation: Heat Fixes

Saturday July 31, 2010

Make sure you’ve completed the How to Use a Microscope and also the Wet Mount and Staining activities before you start here!


If you tried looking at animal cells already, you know that they wiggle and squirm all over the place. And if you tried looking when using the staining technique, you know it only makes things worse.


The heat fix technique is the one you want to use to nail your specimen to the slide and also stain it to bring out the cell structure and nuclei. This is the way scientists can look at things like bacteria.


You’re going to need your microscope, slides, cover slips, eyedropper, toothpicks or tweezers, candle and matches (with adult help), stain (you can use regular iodine or Lugol’s Stain), sugar, yeast, and a container to mix your specimen in. Here’s what you do:


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Microscopes and Telescopes

Wednesday February 3, 2010

Hans Lippershey was the first to peek through his invention of the refractor telescope in 1608, followed closely by Galileo (although Galileo used his telescope for astronomy and Lippershey’s was used for military purposes).  Their telescopes used both convex and concave lenses.

A few years later, Kepler swung into the field and added his own ideas: he used two convex lenses (just like the ones in a hand-held magnifier), and his design the one we still use today. We're going to make a simple microscope and telescope using two lenses, the same way Kepler did.  Only our lenses today are much better quality than the ones he had back then!

You can tell a convex from a concave lens by running your fingers gently over the surface – do you feel a “bump” in the middle of your hand magnifying lens?  You can also gently lay the edge of a business card (which is very straight and softer than a ruler) on the lens to see how it doesn't lay flat against the lens.

Your magnifier has a convex lens – meaning the glass (or plastic) is thicker in the center than around the edges.  The image here shows how a convex lens can turn light to a new direction using refraction. You can read more about refraction here.

A microscope is very similar to the refractor telescope with one simple difference – where you place the focus point.  Instead of bombarding you with words, let’s make a microscope right now so you can see for yourself how it all works together. Are you ready?

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Laser Microscope

Wednesday February 3, 2010

Did you know that you can use a laser to see tiny paramecia in pond water? We’re going to build a simple laser microscope that will shine through a single drop of water and project shadows on a wall or ceiling for us to study.


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