Phase contrast method

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Figure 1: n liquid =1.5446	Figure 2: n liquid =1.5446. Rotation of polarizer.
Figure 3: n liquid =1.528	Figure 4: n liquid =1.5394
	Figure 5: n liquid =1.5528

Quartz crystals in a range of liquids from n= 1.528 to 1.553.

• Figure 1: liquid index matches ordinary index of quartz. Central crystal has ordinary index parallel to polarizer and appears thus with a red -orange halo.

• Figure 2: same index of liquid but rotation of the stage by 90°. The central crystal has now extraordinary index (higher) parallel to polarizer: the halo becomes bright orange.

• Figure 3: the lowest liquid refractive index: all crystals are dark blue with pale yellow halo.

• Figure 4: liquid index slightly lower than ordinary quartz index: all crystals have halo orange to yellow.

• Figure 5: the highest liquid refractive index (equal to the high index of quartz): the central crystal oriented parallel to the optic axis has a red halo (matching for the D line of sodium), other crystals in random orientation appear with a dark halo (brown to black) due to their low index of refraction. With closer examination, some other crystals are also nearly matching.

           Click on images for closer examination.