Topic: Microscope

Aim: How can we measure a cell using a microscope?

Do Now:

1. Copy the aim onto your notes sheet.

2. Complete Microscope Check pink sheet

3. Take out a piece of loose-leaf for today’s notes.

HW: Cells and Cell Processes Exam Review Sheet (BOTH SIDES)

1. Where should the microscope be safely placed?

• On a tabletop or other flat surface.

2. Why is the lowest power objective used first?•It provides a larger field of view.

LOW HIGH

Ruler observed under low power

Ruler observed under high power

LARGER FIELD OF VIEW

SMALLER FIELD OF VIEW

3. Identify the objective that gives a larger field of view.•Low power

LOW HIGH

4. Identify what occurs to the field of view when switching from low to high power.•The field of view decreases.•The amount of light decreases.

5. Identify the part that used to focus the slide when using the 4x and 10x objectives.•Coarse adjustment

6. Identify the part that used to focus the slide when using the 40x objective.

•Fine adjustment

The diagram represents a cell in the field of view of a compound light microscope.

In which direction should the slide be moved on the microscope stage to center the cell in the field of view?

1. toward A

2. toward B

3. toward C

4. toward D

Units to measure cells•Micrometers/Microns •µm•1mm = 1000µm

Cells are so small that even a cluster of these cells from a mouse only measures 50 microns.

The human ovum is typically around between 120 to 150 micrometers which is the largest cell in the human body. It is visible to the human eye under a microscope.

The head of the sperm is on average 5 to 6 micrometers. The flagellum is up to 50 micrometers long.

Paper thickness =about 150 µm

Human hair diameter = 80-100 µm

SHRIMP EGGS

3.2 mm = ? µm 3. 2

3200 µm

0 0

mm um• Move decimal three places to the RIGHT

Are there SI units smaller than micro????

"nano-" = 1/1,000,000,000 (billionth)

"pico-" = 1/1,000,000,000,000 (millionth of a millionth, "micro micro-")

0.7634mm = ? µm

0.7 6 3 4 763.4 µm

789 µm = ? mm 7 8 9 . .789 mm

um mm• Move decimal three places to the LEFT

53.6 µm = ? mm

5 3. 6 .0536

mm

0

1mm

•Field of view =

3200 µm3.2mm =

1.

1000um

500um

1mm =

2.

1000um

2000um2 mm =

2000/2 = 1000

3.

500um

250um

1000um

4.

1000um

500um

2000um

5.

500um

250um

1000um

125um

6.

2500um

1250um

5000um

625um

5mm =

7.

5mm

1000um

= 5000um

8.

7000um

1000um

9.

2000um

400um

10.

Let’s summarize:1. Identify the units used to measure cells.2. Which way do you move the decimal

when converting from mm to um?3. Which way do you move the decimal

when converting from um to mm?4. Describe the two procedures that must be

followed before switching to high power.5. Explain what happens to the amount of

light in your field of view when switching from low to high power.

Determine the length of each cell in um.

Diameter = 1mm Diameter = 2000um

1000um

500um 1000um

500um

= 500um= 500um

Determine the length of each cell in um.

Diameter = 1000um Diameter = 2mm

1000/6= 166.7um

= 2000um

1000um500um

1. Which way should you move the slide to center the cell in the field of view?

Move the slide to the right (towards B)

2. Determine the approximate length of the cell.

a. 300um

b. 500um

c. 700um

d. 1000um

1400um

700um 350um