In a petrographic microscope, the vibration directions of the polarisers and analyser should be

• Parallel to each other

• Perpendicular to each other

• Collinear to each other

• Coplanar to each other

Mineral thin section needs to be kept

• Above polariser and below the analyser

• Above analyser and below the polariser

• Above the analyser and polariser both

• Below the analyser and polariser both

Betrand lens in used in a

• Conoscopic arrangement

• Orthoscopic arrangement

• Petrographic arrangement

• Interferometric arrangement

Accessory plates are inserted

• Below the polariser

• Below the analyser

• Below the thin section

• Above the analyser

In a standard petrographic microscope, 20X objective will magnify an area

• 20 times

• 200 times

• 40000 times

• 20000 times

Opaque minerals are analysed under

• Transmitted light

• Refracted light

• Reflected light

• Diffracted light

which of the following phenomena is not be seen under cross polars

• Inference colours

• Twinkling

• Extinction

• None of above

Light ray that disobey the Snell’s law is called____ray

Extraordinary ray is the slow ray for a

• Optically positive mineral

• Optically negative mineral

• Length fast mineral

• Length slow mineral

Refractive Index of the e-ray will be higher than the o-ray for a

• Optically positive mineral

• Optically negative mineral

• Length fast mineral

• Length slow mineral