IB BIO - U1 L3 P2 - MICROSCOPES AND MICROSCOPE SKILLS (SCIENTIFIC DRAWINGS).

Microscope Types

Ocular lens

Lens in eye piece 10x

Arm

Supports tube and connects it to base

Coarse Adjustment Knob

Moves stage up/down to focus specimen

Fine Adjustment Knob

Precisely focuses specimen

Nose Piece

Holds objective lenses - rotate to change magnification

Stage

Platform where slide is placed

Light Source

Steady light source which illuminates specimen

Base

Supports microscope

Objective Lens

Magnifies specimen - 4X, 10X, 40X and 100X Multiply by 10X (ocular lens) to get total magnification

Diaphragm

Rotating disk under stage - varies amount of light

Stage Clips

Hold slide in place

How to Use Microscope

1. Uncover, plug in and turn on light source

2. Begin with lowest power objective lens - 4X or 10X

3. Place slide on stage - use stage clips to hold in place

4. Look through eye piece and focus specimen by turning course adjustment knob slowly

5. If too dark/bright, adjust diaphragm

6. Move to medium power objective. DON’T touch coarse adjustment knob anymore!

7. Sharply focus specimen using fine adjustment knob

8. Record observations - scientific drawing

Packing Up Microscope

1. Turn objective lens back to low power (4X or 10X)

2. Move stage all the way down and remove slide

3. Wrap cord around base

4. Put on cover

SCIENTIFIC DRAWINGS

• Use a sharp pencil

• Drawing should be neat and simple - don’t include unnecessary detail (like shading/colour)

• Make large drawings (min 1/4 page)

• Include descriptive title at top of page - underline it

• Use a ruler to draw labelling lines - parallel, column, right of F.O.V

• Include total magnification and scale line (1 cm) at bottom right

• Draw only what you see. Not what you THINK you see!!

Determining SIZE of Imaging Using a Scale Bar

• Estimate number of scale bars which fit into image, and estimate length

• Measure length of diagram in millimeters (not cm - because it's easier to divide a larger number and avoid decimals)

• Measure length of scale bar in millimeters

• Divide length of diagram by length of scale bar and multiply by size written on scale bar

Determining MAGNIFICATION Using A Scale Bar

• Measure length of scale bar in mm

• Convert this to same units as written on scale bar - μm

• Divide actual diagram size by measurement written on bar

Determining MAGNIFICATION If Given Actual Size

• Measure image size with a ruler

• Convert actual size and image size to same units

• Divide image size by actual size of specimen

Magnification of a micrograph

• magnification = image size/specimen size

• 1mm=1000μm (micrometres)

Animal Cells Size.

10 to 30 micrometres (µm) in diameter

Plant Cells Size.

10 to 100 micrometres (µm) in diameter

Plant Cells Size.

0.5 to 5 micrometres (µm) in diameter.