different types of oils that can be used with an oio lens
Oil immersion Before the development of synthetic immersion oils in the 1940s, cedar tree oil was widely used. Cedar oil has an index of refraction of approximately 1.516. The numerical aperture of cedar tree oil objectives is generally around 1.3. Cedar oil has a number of disadvantages however: it absorbs blue and ultraviolet light, yellows with age, has sufficient acidity to potentially damage objectives with repeated use (by attacking the cement used to join lenses), and diluting it with solvent changes its viscosity (and refraction index and dispersion). Cedar oil must be removed from the objective immediately after use before it can harden, since removing hardened cedar oil can damage the lens. In modern microscopy synthetic immersion oils are more commonly used, as they eliminate most of these problems.[2] NA values of 1.6 can be achieved with different oils. Unlike natural oils synthetic ones do not harden on the lens and can typically be left on the objective for months at a time.
List of oil fields The list is incomplete; there are more than 65,000 oil and gas fields of all sizes in the world.[1] However, 94% of known oil is concentrated in fewer than 1500 giant and major fields.[2] Most of the world's largest oilfields are located in the Middle East, but there are also supergiant (>10 billion bbls) oilfields in Brazil, Mexico, Venezuela, Kazakhstan, and Russia.