Compound Microscopes

Introduction Light Paths Linear Approximation Pros and Cons

Pros and Cons of the Microscope

Since the invention of the Microscope, it had help so many students and scientists discovered and enhanced our knowledge in basic biology, biomedical research, and medical diagnostics. The technology of Light Microscope have improved far beyond the first microscopes of Robert Hooke and Antoni van Leeuwenhoek. Many improvments on the microscopy techniques and lens engineering all helped to shape today's microscope.

A major problem when observing under compound microscope is that the image doesn't have a big contrast. The general law was enunciated that the apparent brightness of the image as seen by the eye depends on the area of the pupil that is filled with light. Let's assume the pupil of the observer's eye is placed in the eyepiece of the microscope, the only part of the pupil will be filled with light, so the brightness of the image in the microscope can never surpass the natural brightness of the object itself. This is a general law applicable to all optical instruments.

Therefore, there are some techniques to improve this:

  • Fluorescence- use a high energy, short wave-length light source to excite the electrons in the molecules within the speicmen causing them to shift to a higher orbit. When they fall back to the original orbit, they release some energy and make long wave-length light which forms energy.

  • Add dye- treat the specimen with colored pigments or dyes to give some parts of the specimen more contrast.

  • Rheinberg illumination- uses a series of filters to produce an "optical staining" on the specimen.

    One other problem for compound microscope is that it can only magnify till certain extent. Anything smaller then that limit then we can't observe. Therefore, there are other kind of microscope suck as Electron microscopes that can observe even smaller specimens.

    Reference

  • Mirrors, prisms, and lenses, J. P. Southall (1918)
  • College Physics Custom Edition, Serway & Faughn
  • Biology, Fourth Edition, Campbell
    Introduction Light Paths Linear Approximation Pros and Cons

    By James Chien-Chih Yeh 73976995