Microscopes Quiz

What is another problem (besides the small magnification) with light microscopy?

Another problem with light microscopy is that most living cells are nearly transparent. Using chemical stains or dyes can usually solve this problem.

Stains or dyes

Another problem with light microscopy is that most living cells are nearly transparent. Using chemical stains or dyes can usually solve this problem. Some of these stains are so specific that they reveal only certain compounds or structures within the cell.

Resolution

the detail Unfortunately, light itself limits the detail, or resolution, of images in a microscope.

Electrons are easily scattered by __________ __ ___ ___, which means they must be placed in a ______ to be studied with an electron microscope. MORE

Electrons are easily scattered by molecules in the air, which means they must be placed in a vacuum to be studied with an electron microscope. As a result, researchers must chemically preserve their samples. Electron microscopy, then, can only be used to examine non-living cells and tissues.

Scanning Electron Microscope (SEM)

In scanning electron microscopes, a pencil-like beam of electrons is scanned over the surface of a specimen. Because the image is formed at the specimen's surface, samples do not have to be cut into thin slices to be seen. The scanning electron microscope produces stunning 3-D images of a specimen's surface.

Light microscopes can be used to see cells and cell structures as small as ___ __________ of a ______

Light microscopes can be used to see cells and cell structures as small as one millionth of a meter

Why do cells appear to be different colors micrographs from each microscope?

The colors in light micrographs come from the cells themselves, or from the stains and dyes used to highlight them. Electron microscopes, however, are actually black and white. Electrons unlike light don't come in colors. So scientists often use computer techniques to add "false color" to make certain structures stand out.

Objective Lens

The first lens (of a compound light microscope), called the objective lens, is located just above the specimen. Most light microscopes have several objective lenses so that the power of magnification can be varied.

Ocular Lens

The second lens (of a compound light microscope), called the ocular lens, magnifies the image still further.

Compound Light Microscope

The type of microscope you are probably most familiar with is the compound light microscope. A typical light microscope allows light to pass through the specimen and uses two lenses to form an image.

What are the two major types of electron microscopes?

Transmission electron microscope Scanning electron microscope

Transmission Electron Microscope (TEM)

Transmission electron microscopes make it possible to explore cell structures and large protein molecules. But because beams of electrons can only pass through thin samples, cells and tissues must be cut into ultra-thin slices before they can be examined. This is the reason that such images often appear flat and two-dimensional.

Electron Microscopes

What if scientists wanted to study something smaller than one millionth of a meter (how small light microscopes can be used to see), such as a virus or a DNA molecule? For that, they need electron microscopes. Instead of using light, electron microscopes use beams of electrons that are focused by magnetic fields. Electron microscopes offer much higher resolution than light microscopes. Some types of electron microscopes can be used to study cellular structures that are one billionth of a meter in size.

How do you carry a microscope?

You carry a microscope with one hand on the arm and one hand on the base.

How do you focus a microscope?

You put a slide under the microscope, secured by the stage clips, and start on the lowest setting and slowly bring it up to the highest one, to zoom in.

Micrograph

A micrograph is a photo of an object seen through a microscope.

What does a microscope do?

A microscope produces an enlarged image of something very small.

Fluorescence

A powerful variation on these staining techniques uses dyes that give off light of a particular color when viewed under specific wave-lengths of light, a property called fluorescence. Fluorescent dyes can be attached to specific molecules and can then be made visible using a special fluorescence microscope. New techniques, in fact, enable scientists to engineer cells that attach fluorescent labels of different colors to specific molecules as they are produced. Fluorescence microscopy makes it possible to see and identify the locations of these molecules and even allows scientists to watch them move around in a living cell.

Diffracted

Like all forms of radiation, light waves are diffracted, or scattered, as they pass through matter. Because of this light microscopes can produce clear images of objects only to a magnification of about 1000 times.

What would you use a dissecting microscope for?

Looking at bigger objects like pieces of coral. This kind of microscope is plugged into a computer/laptop and the images are produced on the screen. You can then take screenshots.

How do microscopes work?

Most microscopes use lenses to magnify the image of an object by focusing light or electrons.