Refractometry

Question 1

This is a measure of how effective a material is in bending light coming from a vacuum

Answer 1

Index of Refraction

Question 2

Most minerals have indices of refraction in the range of _____ to _______

Answer 2

1.4 to 2.0

Question 3

True or False?

The Index of Refraction is inversely proportional.

Answer 3

True

Question 4

According to Snell’s Law, the light is refracted ________ the normal upon entering a material with a HIGHER index of refraction.

Answer 4

towards

Question 5

According to Snell’s Law, the light is refracted ________ from the normal upon entering a material with a LOWER index of refraction.

Answer 5

away

Question 6

True or False?

Light travels faster if it passes through a material with a high index of refraction

Answer 6

False, light travels slower.

Question 7

What is the simplest method to measure the Index of Refraction of a Mineral?

Answer 7

Immersion Method

Question 8

What is the main tool used in the immersion method?

Answer 8

Immersion Oil

Question 9

This is the degree to which mineral grains stand out from the mounting medium

Answer 9

Relief

Question 10

A degree of relief observed in mineral grains that are distinct or clear.

Answer 10

High Relief

Question 11

In HIGH relief, the mineral and oil/balsam indices differ by how much?

Answer 11

0.12 or more

Question 12

A degree of relief observed in mineral grains that are a bit unclear but still distinguishable.

Answer 12

Moderate Relief

Question 13

In MODERATE relief, the mineral and oil/balsam indices differ by how much?

Answer 13

0.04 to 0.12

Question 14

A degree of relief observed in mineral grains that are almost indistinguishable.

Answer 14

Low Relief

Question 15

In LOW relief, the mineral and oil/balsam indices differ by how much?

Answer 15

0.04

Question 16

If the index refraction of the oil is EQUAL TO the mineral, what happens to the appearance of the mineral grain?

Answer 16

The Grain does not stand out

Question 17

If the index refraction of the oil is NOT EQUAL TO the mineral, what happens to the appearance of the mineral grain?

Answer 17

The Grain appears to stand out

Question 18

True or False?

The relief of anisotropic/birefringent minerals does not change when the stage is rotated.

Answer 18

False, their relief may change.

Question 19

What is the type of relief when the index of mineral > index of surroundings?

Answer 19

Positive Relief

Question 20

What is the type of relief when the index of mineral < index of surroundings?

Answer 20

Negative Relief

Question 21

This is a band of light along the grain boundaries when slightly out of focus

Answer 21

Becke Line

Question 22

What happens to the Becke Line when the focal distance is increased?

Answer 22

The Becke line goes to the medium with a higher index of refraction.

Question 23

This is an effect when thinner mineral fragments on the edges act as crude lenses

Answer 23

Lens Effects

Question 24

This is an effect when the converging light hitting the vertical grain edges is either refracted or internally reflected.

Answer 24

Internal Reflection Effect

Question 25

What do you call the technique whereby light is projected at the specimen from sideways to reveal features with higher contrast compared to when viewed with brightfield illumination?

Answer 25

Oblique Illumination Method

Question 26

What is the index refraction of Balsam?

Answer 26

1.540

Question 27

What is the index refraction of Quartz?

Answer 27

1.544 to 1.553

Question 28

True or False? It is possible to get the exact index of refraction of a mineral in a rock with multiple minerals.

Answer 28

False

Question 29

What is Garnet's relief?

Answer 29

High Relief

Question 30

What is the degree of relief of a mineral with a difference in relief from balsam of 0.01?

Answer 30

Low Relief

Question 31

The velocity of light as it passes through a mineral is compared to the velocity of light in ____________ to get the index of refraction.

Answer 31

Vacuum

Question 32

A mineral with a lower index of refraction exhibits ______ towards the ________

Answer 32

BRIGHT MARGINS towards the BRIGHT FIELD

Question 33

True or False? Light will bend closer to the normal as it passes through a medium of greater refractive index.

Answer 33

True

Question 34

What is the relief of Quartz?

Answer 34

Low Relief

Question 35

True or False? A mineral with a negative relief has an index of refraction less than its surroundings.

Answer 35

True