Microscope Magnification Activity
Goal: Calculate magnification, actual size and image size with M = image size ÷ actual size, convert between millimeters and micrometers, and work out total microscope magnification.
What to do
- On Find actual size, press “20 mm drawing at 400×” and record the actual size.
- Switch to Find magnification and press “Red blood cell: 7.5 µm drawn 7.5 mm wide”. Record the magnification.
- Switch to Find image size and press “Bacterium: 2 µm at 1,000×”. Record the image size.
- Switch to Total magnification and press “10× eyepiece · 40× objective”, then “10× eyepiece · 4× scanning objective”. Record the total magnification and field of view each time.
Record your results
| What to find | Your result |
|---|---|
| Actual size of a 20 mm drawing at 400× | |
| Magnification of a 7.5 µm cell drawn 7.5 mm wide | |
| Image size of a 2 µm bacterium at 1,000× | |
| Total magnification: 10× eyepiece, 40× objective | |
| Field of view at that magnification | |
| Total magnification: 10× eyepiece, 4× objective | |
| Field of view at that magnification |
Questions
A drawing of a cell is 20 mm wide at 400× magnification. Show how to find the cell’s actual size in micrometers.
A red blood cell 7.5 µm across is drawn 7.5 mm wide. A student says the magnification is 1×. What mistake did they make, and what is the right answer?
How large does a 2 µm bacterium appear at 1,000×?
What is the total magnification with a 10× eyepiece and a 40× objective? How many 50 µm cells fit across the 450 µm field of view?
When you switch from the 4× objective to the 40× objective, the magnification rises 10 times. What happens to the field of view?
Challenge: a scale bar on a micrograph is labeled 20 µm and measures 8 mm on the page. What is the magnification?
Free from Biology Lab · thebiologylab.org · MS-LS1-1: Conduct an investigation to provide evidence that living things are made of cells.