Microscopes

Question 1

What are key terms related to microscopy?

Answer 1

• Object: Material placed under the microscope
• Image: How the object appears under the microscope
• Magnification: How many times larger the image is compared to the object
• Resolution: Ability to distinguish between two objects close together

Question 2

How do you calculate magnification?

Answer 2

Magnification = Size of image ÷ Size of object

Question 3

How do you convert between measurement units?

Answer 3

• 1mm = 1000μm
• 1μm = 1000nm
• 1nm = 1000pm

Question 4

What are the steps to measure cell size using a scale bar?

Answer 4

• Measure the length of the scale bar on the image
• Divide by the given scale bar value
• Multiply by the actual size of the object

Question 5

How do you calculate total magnification of a microscope?

Answer 5

Total magnification = Eyepiece magnification × Objective magnification

Example: Eyepiece (×10) × Objective (×40) = ×400 magnification.

Question 6

What is the difference between magnification and resolution?

Answer 6

• Magnification: How much larger the image appears compared to the object
• Resolution: How clearly two close objects can be distinguished

Question 7

What are the advantages and disadvantages of a Light Microscope?

Answer 7

Advantages:
- Can observe living cells
- Easy to use
- Cheap

Disadvantages:
- Low magnification (×1500)
- Low resolution (0.2μm)
- Cannot see most organelles

Question 8

What are the advantages and disadvantages of TEM?

Answer 8

Advantages:
- High magnification (up to ×500,000)
- High resolution (0.05-2nm)
- Detailed internal structures

Disadvantages:
- Only dead samples
- Vacuum required
- Expensive
- Preparation can cause artefacts

Question 9

What are the advantages and disadvantages of SEM?

Answer 9

Advantages:
- High magnification (up to ×500,000)
- Produces 3D images
- Good surface detail

Disadvantages:
- Cannot see internal structures
- Expensive
- Requires vacuum

Question 10

What are the advantages and disadvantages of Laser Scanning Microscope?

Answer 10

Advantages:
- Can observe living cells
- 3D imaging
- High resolutionrrtyuioptppiiiii

Disadvantages:
- More expensive than light microscopes
- Complex to use

Question 11

What is the purpose of staining in microscopy?

Answer 11

• Increases contrast to make structures more visible
• Differential staining distinguishes between different structures

Example: Haematoxylin stains nuclei purple, eosin stains cytoplasm pink.

Question 12

What are common stains used in microscopy?

Answer 12

• Acetic orcein: stains chromosomes dark red
• Eosin: Stains cytoplasm dark red or pink
• Iodine: Stains starch blue-black
• Iodine in potassium iodide: Stains cellulose yellow
• Haematoxylin: Stains DNA/RNA purple-blue
• Methylene blue: Stains DNA blue

Question 13

How is differential staining used in bacteria?

Answer 13

Used to differentiate bacteria with or without slime capsules

Steps:
1. Stain with crystal orange
2. Add melanin solution
3. Add iodine solution to remove excess stain
4. Add sacharin to stain bacteria black- without capsule

Question 14

What are the key rules for scientific drawings?

Answer 14

• Use white and unlined paper
• Draw with sharp pencil
• No shading or colour
• Label neatly with horizontal lines but with no arrows
• Provide title and magnification
• Ensure proportion and clarity of structures