Chapter 2.2 - Microscopes

Question 1

What are the principles of light microscopes?

Answer 1

• Uses light to form an image
• Light that passes through or reflects from the surface of the specimen is seen

Question 2

What is the functionality of light microscopes?

Answer 2

• Magnification to 2000 x
• Resolution to 200nm
• Living and non-living specimens can be observed
• 2D colour images

Question 3

How do you use a light microscope? (5)

Answer 3

1. Place the specimen on a slide which is fixed to a stage, and clip it in place, stain if needed
2. Rotate the revolving nosepiece to the lowest power objective lens is over the specimen
3. Adjust the coarse focus knob until the image is clear and in focus
4. Adjust the iris diaphragm for optimum light
5. Make sure the object is directly above the hole in the stage, rotate the nosepiece to the next greatest lens over the specimen. Look down the ocular tube and use the fine focus knob to focus the image

Question 4

What are the advantages of light microscopes?

Answer 4

• Small and relatively cheap
• Specimen preparation can be straightforward enough to perform in a school laboratory
• Produce colour images
• 2D

Question 5

What are the principles of transmission electron microscopes?

Answer 5

• Uses electrons to form an image
• Electrons that pass through the specimen are detected, creating contrast

Question 6

What is the functionality of transmission electron microscopes?

Answer 6

• Magnification to 1 000 000 x
• Resolution to 0.2nm
• Only dead or non-living specimens can be used

Question 7

What type of images so TEMs produce?

Answer 7

• High resolution
• Internal structures within cells and organelles can be seen
• 2D

Question 8

What are the principles of scanning electron microscopes?

Answer 8

• Uses electrons to form an image
• Electrons that are reflected from the surface on the specimen are detected

Question 9

What is the functionality of scanning electron microscopes?

Answer 9

• Magnification to 1 000 000 x
• Resolution to 3-20nm
• Only dead or non-living specimens can be used

Question 10

What type of images do SEMs produce?

Answer 10

• 3D
• Shows the surface of specimens
• Lower resolution than TEMs

Question 11

What are the principles of laser scanning confocal microscopes?

Answer 11

• Uses a laser bean to scan an object pixel by pixel, creating a 3D image of the reflected photons.
• 2D images of higher resolution can also be produced

Question 12

What is the functionality of laser scanning confocal microscopes?

Answer 12

• Requires a compromise between resolution, scan time, and photo destruction(laser can damage of the specimen
• Fluorescent dyes can be used to tag specific molecules