microscope question?

Question

why do specimens in slides in the microscope have to be thin?

Answer 1

Actually, specimens don't *have* to be thin unless you're viewing with transmitted light (as most compound microscopes are set up for). If you're viewing with reflected light, you can have thick specimens.

A commercial example of a reflected light compound scope:
http://www.martinmicroscope.com/MicroscopePages/RLbrightfield.htm

More here: http://www.microscopy-uk.org.uk/mag/indexmag.html?http://www.microscopy-uk.org.uk/mag/art98/incid1.html

Answer 2

Two reasons:

1. The specimen must be thin enough for light to pass through it so the observer would be able to see it.
2. If you are trying to see cells, the specimen should be about one cell thick to avoid complicated views of too many cell layers at a time. Just picture how it would look if your teacher put two or three transparencies on the overhead projector at one time. That's like looking through too many cell layers.