Light Microscopy.

Question 1

How does a Light Microscope work?

Answer 1

• Light passed through an object placed on slide on stage
• then through glass objective lens + eyepiece lens.
• Lenses magnify the object= when you view through eyepiece- more detail.

Question 2

Steps to Use a Light Microscope:

Answer 2

1. Move stage to its lowest position.
2. Select objective lens with lowest magnification.
3. Place slide with cells on, on stage.
4. Raise stage to highest position, make sure slide does not touch the lens.
5. Lower stage slowly using the coarse focus knob until object seen (will normally be blurred).
6. Turn fine focus knob slowly until object comes into clear focus.
7. Switch to higher magnification objective lens without moving the stage to see more detail. Use fine focus knob to bring object into clear focus again.

Question 3

What is the formula for total magnification?

Answer 3

Eyepiece Lens magnification x Objective Lens magnification.

Question 4

Why do scientists stain cells?

Answer 4

• Many cells are colourless.
• Scientists often stain them to make them easier to observe.
• Some stains colour whole cell
• Others highlight specific subcellular structures.

Question 5

What stain makes it easier to see the nucleus of an animal cell?

Answer 5

Methylene Blue.

Question 6

What stain makes it easier to see plant cell nuclei?

Answer 6

lodine.

Question 7

What stain makes it easier to see bacterial cell walls?

Answer 7

Crystal Violet.

Question 8

How does one apply a stain?

Answer 8

1. Place cells on glass slide.
2. Add one drop of stain.
3. Place coverslip on top.
4. Tap coverslip gently with pencil to remove air bubbles.

Question 9

List all 7 components of a light microscope:

Answer 9

eyepiece lens
• obiective lens
• coarse focussing knob
• stage
• fine focussing knob
• (a slide can be used which is placed on the stage)
• light source