Microscopy
Eye feel itchy
Right at this moment in time there are hundreds of tiny bugs living peacefully under your eyelashes. They’re called follicle mites (Demodex folliculorum, to be precise) and are a bit like fleas (except they can’t jump quite so high). You’ll have a few up your nose and in your ear canals, too. The female mites will be laying eggs – about 25 in each follicle – while feeding on your greasy secretions. When the eggs are hatched and the young mites grow up, they’ll leave the follicle, mate and find a new follicle. All this happens in a couple of weeks.
 |
You’re not a particularly dirty teenager. Everyone’s got them. Don’t bother trying to look for them. They’re microscopic. But don’t panic because they’re also harmless!
You probably wish you didn’t know all that. You may even feel quite itchy. Well, hundreds of years ago nobody could have known about these mites. That’s because anything microscopic can’t be seen with the naked eye. So before microscopes were invented scientists knew nothing of the microscopic world.
Light microscopy
When you think “microscope”, you probably think of light microscopes (sometimes called compound microscopes). These are the ones used in your school lab. They’re also the ones you need to know how to set up and use to pass your GCSE Applied Science.
The magnifying power of a light microscope is equal to the power of the eyepiece lens multiplied by the power of the objective lens. The very best light microscopes can produce images 1500x life size.
School light microscopes often have a 10x eyepiece lens, and 5x, 10x and 40x objective lenses. So, the highest magnification would be 400x (10 x 40).
The microscope won’t have, for example, a 16x eyepiece lens and 7x objective lens, because lenses aren’t made to those values. Microscope manufacturers the world over arrived at a number of set values many years ago. The screw threads also meet a standard set by the Royal Microscopy Society.
Spit and spot ovulation
Women can work out if they’re ovulating and ready to conceive by spitting on a small light microscope.
They do so using a home testing kit, which is about the size of a lipstick holder. It’s a small light microscope that can magnify up to around 60x life size.
Women’s saliva changes appearance when they ovulate, and the microscope is powerful enough to make the distinction.