Module 2 - MIcroscopes

Question 1

What microscope is useful for passing through specimens?

Answer 1

Compound light microscope

Question 2

What are the advantages of a light microscope?

Answer 2

• Inexpensive
• Portable
• Simple sample prep
• Living or dead specimens

Question 3

How does a laser scanning confocal microscope work?

Answer 3

• Produces a focused source of light and rejects out-of-focus light, which provides the ability to image deep into tissues with high resolution.
• Emitted light from the specimen is filtered through a pinhole so only light radiated very close to the focal plane is detected.
• A 3D image is created at different focal planes.

Question 4

What are the advantages of a laser-scanning confocal microscope?

Answer 4

• Simple sample preparation
• Living or dead specimens

Question 5

What are the disadvantages of a laser-scanning confocal microscope?

Answer 5

• Low magnification and resolution compared to electron mics
• Expensive to buy

Question 6

How does a transmission electron microscope work?

Answer 6

• Electrons are transmitted through a specimen and focussed to produce an image
• Specimen is viewed in a vacuum to ensure the electron beams travel in a straight line.

Question 7

How can a higher resolution be achieved in a TEM and an SEM?

Answer 7

Because electrons have a much smaller wavelength than light.

Question 8

What are the disadvantages of TEM and SEM?

Answer 8

• Expensive to buy and operate
• Large and needs installation
• Complex sample preparation
• Risk of artifacts
• Black and white images
• Dead specimens

Question 9

What is the difference between SEM and TEM?

Answer 9

SEM beams electrons across the surface of the specimen and images are collected via the reflection of electrons whilst in TEM, electrons are transmitted through the specimen to create an image.

Question 10

What are the advantages of SEM?

Answer 10

High resolution and magnification
and 3D images are obtained which show the appearance of organisms

Question 11

What are the advantages of TEM?

Answer 11

High resolution and magnification.

Question 12

How does a scanning electron microscope work?

Answer 12

• A beam of electrons is sent across the surface of a specimen and the reflected electrons are collected.
• Produces 3D surface images

Question 13

When is a dry mount used in microscopy?

Answer 13

Useful for observing thin and small objects .e.g. parts of insects, pollen and hairs

Question 14

How do you prepare a dry mount specimen?

Answer 14

• If the specimen is thick, slice it up to make it more thin.
• Use tweezers to place it on the slide
• Place a cover slip on top.

Question 15

When is a wet mount used in microscopy?

Answer 15

Useful when the specimen is wet or is in a liquid e.g. tiny aquatic organisms

Question 16

How do you prepare a wet mount specimen?

Answer 16

• Place a small drop of water on the slide
• Place the specimen on top of this water drop
• When inserting the coverslip, make sure you stand it up straight, then carefully lower it by tilting it to avoid air bubbles
• Add a stain to the specimen to view it more clearly.

Question 17

What is an eyepiece graticule?

Answer 17

A transparent ruler that is fitted in the microscope which offers a scale.

Question 18

What is a stage micrometer?

Answer 18

A microscope slide that offers an accurate scale (units) and is used to work out the value of divisions on the eyepiece graticule