2.1.1 Microscopes

Question 1

What is magnification?

Answer 1

The number of times larger an image appears, compared with the size of the original object

Question 2

What type of magnification does a microscope produce?

Answer 2

Linear magnification, meaning that if a specimen is seen magnified x100, it appears to be 100 times wider and 100 times longer than it really is.

Question 3

What is resolution?

Answer 3

The clarity of an image; the higher the resolution, the clearer the image.

Question 4

What is an optical microscope and what are they used for?

Answer 4

They are microscopes that uses visible light and lenses to magnify an image and are used to see some of the larger structures in the cells.

Question 5

What are the advantages of optical microscopes?

Answer 5

• Cheap
• Easy to use
• Portable and able to be used in the field as well as in labs
• Able to be used to study whole living specimens

Question 6

What is a disadvantage of optical microscopes?

Answer 6

Has a low/limited resolution of 2μm

Question 7

What is the magnification of an optical microscope?

Answer 7

X1500

Question 8

How do you calculate the total magnification?

Answer 8

Total magnification = magnifying power of the objective lens x magnifying power of the eyepiece lens

Question 9

What is a photomicrograph?

Answer 9

Photograph of the image seen using an optical microscope.

Question 10

What are laser scanning microscopes?

Answer 10

They use laser light to scan an object point by point and assemble, by computer the pixel information into one image displayed on a computer screen.

Question 11

What is another name for a laser scanning microscope?

Answer 11

Confocal microscope.

Question 12

What are the advantages of laser scanning microscopes?

Answer 12

• The images produced are high resolution and show high contrast.
• They can focus on structures at different depths within a specimen, so they can be used to clearly observe whole living specimens as well as cells.

Question 13

What are electron microscopes?

Answer 13

They use a beam of fast-travelling electrons with wavelength of about 0.004nm.

Question 14

What is an advantage of electron microscopes?

Answer 14

They have a higher resolution than optical microscopes and can be used to give clear and highly magnified images.

Question 15

How do transmission electron microscopes work?

Answer 15

• The specimen has to be chemically fixed by being dehydrated and stained with metallic salt stains.
• The beam of electrons passes through the specimen, which is stain with metal salts.
• Some electrons pass through and are focused on the screen or photographic plate.
• The electron form a 2D black-and-white image

Question 16

1What are photographs produced by an electron microscope called?

Answer 16

Electron micrograph.

Question 17

What is the magnification of electron microscopes?

Answer 17

Up to x2million (x50million being developed)

Question 18

How does a scanning electron microscope work?

Answer 18

• Electrons do not pass through the specimen, which Is whole, but cause secondary electrons to bounce off the specimen’s surface and be focused onto a screen. The specimen is placed in a vacuum and is coated with a fine film of metal.

Question 19

What kind of image is produced by a scanning electron microscope?

Answer 19

3D image

Question 20

What is the magnification of scanning electron microscopes?

Answer 20

From x15 to x200,000

Question 21

What are the disadvantages of electron microscopes?

Answer 21

• Very large and expensive
• Need a great deal of skill and training to use
• Metallic salt stains used for staining the specimens may be potentially hazardous to the user