To correctly set up a light microscope to observe human blood.
Microscopy is used in many areas of biological science and is an extremely useful tool in aiding research, and is particularly valuable in the study of the components of organisms. Microscopes work using a complex coordinated system of lenses in such a way that a magnified image of a specimen is seen many times its actual size.
Obtaining a clear image is crucial and is dependant on several things; correct usage of the microscope (which will be explained in the method section of this report), good resolution and good contrast.
Good resolution is acquired by keeping all lenses clean and depends on the wavelength of the illumination. Due to the wave nature of light, it cannot be focussed beyond 200nm and therefore features beyond this would be indistinguishable. Electron microscopes have shorter wavelengths, but a light microscope is more appropriate for observing whole blood cells.
Good contrast is essential for the comparison between areas of the specimen, such as light areas vs. dark areas. A problem that arises is that most cells are different shades of grey and to increase the contrast, specimens are stained. The stain used for blood is Leishmann's, a mixture of two different stains: methylene blue, which stains nuclei and eosin, which stains the cytoplasm. This is useful in observing blood cells as it helps to distinguish between erythrocytes, which have no nuclei and leucocytes, which have varying types of nuclei.
Method.
1) The microscope was switched on at the mains and on the back of the base.
2) A stained section of ileum was placed on the stage and positioned using the clips of the mechanical stage.
3) The low power objective (x 10) was rotated into position.
4) The eyepiece lenses were then adjusted to suit eye spacing.
5) The stage was brought as close to the low power objective lens as possible by turning the coarse focus clockwise.