1Made of cells
All living things are made of cells, the building blocks of life. Some living things are a single cell; you are made of trillions. Most cells are too small to see without a microscope.
cell
Lesson 1.1 notes
Looking at cells
All living things are made of cells. Use a light microscope to see them: focus it, make a slide, work out the magnification and draw what you see.
2The light microscope
A light microscope shines light up through a thin specimen on a slide, which sits on the stage. The objective lens and the eyepiece lens magnify it.
light microscopespecimenstageobjective lenseyepiece lens
3Focusing
Start on the lowest-power lens. Watching from the side, bring the slide up close with the coarse focus. Then look through and lower it slowly until the cells appear. Sharpen with the fine focus.
coarse focusfine focus
4Making a slide
Lay thin onion skin on a slide and add a drop of stain, such as iodine, so the parts show up. Lower a cover slip at an angle to keep out air bubbles.
staincover slip
5Magnification
Multiply the two lenses to get the total magnification. A ×10 eyepiece lens with a ×40 objective lens gives ×10 × 40 = ×400: the cells look 400 times bigger across.
magnification
6More power, less to see
With a higher-power lens the cells look bigger, but the field of view (the part of the slide you can see) is smaller, so fewer cells fit in it.
field of view
7Drawing cells
Draw what you see with a sharp pencil: clear outlines and no shading. Label the parts with straight ruled lines, and add a title and the magnification.
scientific drawing
Explore: Microscope lab
Pick a slide and an objective lens, then turn the coarse and fine focus until the cells are sharp. Take care at high power: the lens is very close to the slide.
Common mistake: Magnifications multiply, they don't add
A ×10 eyepiece lens with a ×40 objective lens gives ×10 × 40 = ×400, not ×50. The eyepiece lens magnifies the image that the objective lens has already magnified.
Remember
- All living things are made of cells. Most cells are far too small to see without a microscope.
- Start on the lowest-power objective lens. Focus with the coarse focus, then make the image sharp with the fine focus.
- total magnification = eyepiece lens × objective lens, so ×10 and ×40 give ×400.
Going further at GCSE
GCSE: Using a microscope → GCSE: Magnification and cell size →