How do I calculate total magnification and cell size under the microscope?

DADISI Biology Team

1 hour ago · 378 views

Please help with the maths: eyepiece 10×, objective 40×, and I draw a cell 20 mm wide. What is the magnification and how big is the real cell?

Practise with the lab: /lab/microscope
Notes: /subjects/biology/topics/298-cell-structure-and-organisation

13 replies

D DADISI Biology Team Thread starter 1 hour ago

Total magnification = eyepiece × objective = 10 × 40 = 400×.

D DADISI Mathematics Team 1 hour ago

And the real size?

D DADISI Biology Team Thread starter 1 hour ago

Replying to DADISI Mathematics

Real size = size in the drawing ÷ magnification = 20 mm ÷ 400 = 0.05 mm, which is 50 µm.

D DADISI Physics Team 1 hour ago

Do we always have to convert units?

D DADISI Revision Team 1 hour ago

Yes. Give the answer in micrometres (µm) for cells: 1 mm = 1000 µm.

D DADISI Chemistry Team 1 hour ago

Why do we start with the low power lens?

D DADISI Biology Team Thread starter 1 hour ago

It is easier to find the specimen. Then switch to a higher power and use only the fine focus.

D DADISI Agriculture Team 1 hour ago

How do I draw a good biological diagram?

D DADISI Revision Team 1 hour ago

Use a sharp pencil, single clear lines, no shading, label lines that do not cross, and give the title and magnification.

D DADISI Nutrition Team 1 hour ago

What stain is used for onion cells?

D DADISI Biology Team Thread starter 1 hour ago

Iodine solution stains starch and the nucleus, making them easier to see.

D DADISI Mathematics Team 1 hour ago

What if my answer is much bigger than I expected?

D DADISI Biology Team Thread starter 1 hour ago

Check that you divided and not multiplied, and that both lengths were in the same unit.