Scope:

ASTM D542 test method provides a procedure for measuring the index of refraction of transparent organic plastic materials. The index of refraction is the ratio of light velocity in vacuum to light velocity in a transparent substance. Similarly, it can be used to measure the bent angle of a light beam as it travels through a transparent medium. The index of refraction is used in the construction of optical lenses as well as a quality management check on clear plastics.

Test Procedure:

A small drop of contacting liquid is mounted in the middle of the prism for the ASTM D542 test. Then the sample is kept on the prism. To coordinate the sample through the eyepiece, the light source, index arm, and compensator drum are all configured. The refractometer then provides a digital read-out of the refractive index.

Specimen size:

Usually a sample with 6.312.7 mm dimensions and polished flat surface is used for the test. 

Data:

Index of Refraction 

Conclusion:

ASTM D542 is a standard test method for index of refraction of transparent organic plastics.