Reflection and refraction at a plane surface

Material Refractive index (at 532 nm) Internal transmission range (nm) Thermal expansion coefficient (10- K ) 

Finally, the material s ability to withstand high differentials in pressure is important for optical components used in connection with vacuum chambers (transition from ambient to very low pressures). 

As with mechanical characteristics, chemical characteristics should be taken into account for optics used in harsh conditions. Characteristics, such as resistance to acids, can severely affect durability and elements made from hygroscopic materials (such materials are sometimes used for IR light applications) might cloud over due to hydroxide corrosion. In addition, the surface of a component can become contaminated from its exposure to polluted atmospheres (e.g. generating chemical films) or grease. 

Regardless of all these remarks, the most important properties of an optical material are, by and large, internal and external transmittance, surface reflectance, and its refractive index however, the non-optical properties are also important when incorporating them into specific experimental set-ups. Some of the properties and characteristics of common optical materials are summarized in Table 10.2. 

When light strikes the surface of any object, some of the light is reflected, the object absorbs some, and some is transmitted through the object, as highlighted above. For simplicity, in the following treatment we will assume that the (refracted) transmitted light does not suffer absorption losses, so that we can concen- 

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