6. Calculate the relief of diamond (n-2.417) mounted in epoxy (n 1.540) and stat

Question

6. Calculate the relief of diamond (n-2.417) mounted in epoxy (n 1.540) and state whether it is high, moderate, or low (show your workl). (4) A photograph of a quartz-rich rock taken in cross-polarized light is provided. Quartz grains are either labeled with "Q" or occur as larger, equant crystals (ignore "C" and arrows). Explain how you would determine which quartz crystal is oriented so that you are looking down the optic axis, and explain why this orientation yields its observed optical properties. (6) 7.

Explanation / Answer

6]

The relief of diamond = Refractive index of diamond - refractive index of epoxy

= 2.417-1.540

= 0.877

The relief of diamond is high.

7]

The quartz grains which appear darker are oriented such that we are looking down the optic axis. This is because the darker colours indicate that the birefringence is minimum or close to zero. Optic axis is the axis where the birefringence is zero. Hence the orientation yields darker colour .

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