Electric polarization

1590s: Dutch spectacle maker Janssen experimented with putting lenses in tubes. He made the first compound microscope. None of these microscopes have survived, but they are thought to have magnified from ×3 to ×9.

The magnification of a lens is shown by a multiplication sign followed by the amount the lens magnifies. So a lens magnifying ten times would be ×10. The total magnification of a microscope is:

Polarization

In most microscopes, there is a choice of objectives to use. Magnification can therefore be varied, according to the size of the specimen to be viewed and the level of detail required.

Linear polarization

1650s: British scientist, Robert Hooke (also famous for his law of elasticity in Physics) observed and drew cells using a compound microscopeclosecompound microscopeA microscope in which the lens is close to the sample being magnified..

We need microscopes to study most cells. Microscopes are used to produce magnified images. There are two main types of microscope:

Light and electron microscopes allow us to see inside cells. Plant, animal and bacterial cells have smaller components each with a specific function.

Late 1600s: Dutch scientist Antonie van Leeuwenhoek constructed a microscope with a single spherical lens. It magnified up to ×275.

Circularly polarizedlight

The optical quality of lenses increased and the microscopes are similar to the ones we use today. Throughout their development, the magnification of light microscopescloselight microscopeDevice that uses visible light and a series of lenses to produce an enlarged image of an object. has increased, but very high magnifications are not possible. The maximum magnification of a light microscope is around x2000. However, most of the microscopes that are used in schools can only reach x400 magnification.

Light can be described as an electromagnetic wave traveling through space. For purposes of ellipsometry, it is adequate to discuss the waves’s electric field behavior in space and time, also known as polarization. The electric field of a wave is always orthogonal to the propagation direction. Therefore, a wave traveling along the z-direction can be described by its x- and y- components. When the light has completely random orientation and phase, it is considered unpolarized. For ellipsometry, however, we are interested in the kind of electric field that follows a specific path and traces out a distinct shape at any point. This is known as polarized light. When two orthogonal light waves are in-phase, the resulting light will be linearly polarized. The relative amplitudes determine the resulting orientation. If the orthogonal waves are 90° out-of-phase and equal in amplitude, the resultant light is circularly polarized. The most common polarization is “elliptical”, one that combines orthogonal waves of arbitrary amplitude and phase. This is where ellipsometry gets its name.

Glass was developed by the Romans in the first century. Since then, scientists have been trying to magnify objects. No-one knows who first invented the microscope, but there have been key stages in their development: