5.Optical Properties of Gems – Nature of Light

Welcome to your Module - 5 - Optical Properties of Gems-Gemology and Optical Phenomena

1. What does total internal reflection contribute to in a gemstone?

The Importance of Light in Gemology

a) Luster

b) Transparency

c) Brilliance

d) Pleochroism

2. Why is polarization important in gemology?

a) It enhances luster

b) It reveals internal structures

c) It changes color perception

d) It causes asterism

3. Which optical phenomenon is crucial for distinguishing between gemstones and imitations?

a) Asterism

b) Aventurescence

c) Dispersion

d) Pleochroism

4. What is the primary role of transparency in gemstone evaluation?

a) Enhancing color

b) Reflecting light

c) Facilitating internal reflections

d) Allowing light to pass through without absorption

5. What aspect of gemstone optics does dispersion affect?

a) Luster

b) Brilliance

c) Color separation

d) Transparency

6. Which color has the longest wavelength in the visible spectrum?

Nature of Visible Light in Gemology

a) Red

b) Green

c) Blue

d) Violet

7. What is the speed of light in a vacuum?

a) 300,000 km/s

b) 300,000 m/s

c) 3,000,000 km/s

d) 3,000,000 m/s

8. What property of light determines its directionality in gemology?

a) Dispersion

b) Refraction

c) Polarization

d) Absorption

9. Which gemstone property is responsible for the playofcolor in opals?

a) Iridescence

b) Pleochroism

c) Refraction

d) Dispersion

11. What is the phenomenon where light bounces off the surface of a gemstone?

Transparency, Reflection and Dispersion in Gemology

a) Refraction

b) Dispersion

c) Reflection

d) Polarization

12. Which property of a gemstone allows light to pass through without significant absorption or reflection?

a) Transparency

b) Refraction

c) Reflection

d) Dispersion

13. What does dispersion refer to in gemology?

a) Reflection of light off the surface

b) Absorption of light by the gemstone

c) Separation of light into its component colors

d) Passing of light through the gemstone without reflection

14. Which optical phenomenon causes a gemstone to show different colors when viewed from different angles?

a) Pleochroism

b) Iridescence

d) Refraction

15. What is the term for the bending of light as it passes from one medium to another?

a) Reflection

b) Dispersion

c) Refraction

d) Absorption

16. What is total internal reflection?

Total Internal Reflection in Gemology

a) Complete absorption of light within a gemstone

b) Reflection of light at the gemstone's surface

c) Reflection of light inside the gemstone due to critical angle

d) Dispersion of light into different colors

17. In which type of gemstone is total internal reflection important for enhancing brilliance?

a) Faceted gemstones

b) Cabochoncut gemstones

c) Opaque gemstones

d) Rough gemstones

18. What happens to light when it hits the boundary between a gemstone and air at an angle greater than the critical angle?

a) It passes through the gemstone

b) It reflects off the surface of the gemstone

c) It reflects inside the gemstone

d) It changes color

19. Why is total internal reflection important in gemology?

a) It enhances luster and brilliance

b) It causes pleochroism

c) It increases transparency

d) It creates interference patterns

20. What is the critical angle for total internal reflection in gemstones?

a) 90 degrees

b) 180 degrees

c) 45 degrees

d) It varies depending on the gemstone

21. What is luster in gemology?

Luster and Brilliance in Gemology

a) The amount of light that a gemstone reflects from its surface

b) The sparkle and brightness of a gemstone

c) The dispersion of light into different colors

d) The transparency of a gemstone

22. Which property of a gemstone is responsible for its brilliance?

a) Reflection

b) Dispersion

c) Refraction

d) Total internal reflection

23. Which type of cut is most likely to maximize brilliance in a gemstone?

a) Cabochon

b) Brilliant cut (round)

c) Rose cut

d) Emerald cut

24. What is the term for the reflection of light from the surface of a gemstone?

a) Refraction

b) Dispersion

c) Reflection

d) Polarization

25. How does the luster of a gemstone contribute to its visual appeal?

a) By enhancing its color

b) By increasing its transparency

c) By improving its brilliance and sparkle

d) By creating interference patterns

26. Which type of minerals have the same optical properties in all directions?

Isotropic and Anisotropic Behavior, Pleochroism, Polarization, Optic Axes, and Interference

a) Isotropic

b) Anisotropic

c) Polycrystalline

d) Amorphous

27. What is pleochroism in gemology?

a) The same color seen from all angles

b) Different colors seen from different angles

c) A starshaped pattern of light

d) A glittery effect due to reflective inclusions

28. What is the property of light that refers to its orientation in specific directions?

a) Dispersion

b) Refraction

c) Polarization

d) Reflection

29. What are optic axes in anisotropic minerals?

a) Directions where light travels without experiencing birefringence

b) Directions where light is absorbed

c) Directions where light is refracted

d) Directions where light is reflected

30. What causes interference patterns in gemstones?

a) Reflection from the gemstone's surface

b) Dispersion of light into different colors

c) Diffraction of light within the gemstone

d) Polarization of light

31. What is the phenomenon where a gemstone shows a narrow band of light across its surface?

Special Optical Phenomena in Gemology

a) Asterism

b) Chatoyancy

c) Adularescence

d) Iridescence

32. Which optical phenomenon causes a gemstone to display a play of colors when viewed from different angles?

a) Asterism

b) Chatoyancy

c) Labradorescence

d) Aventurescence

33. What is the effect called where a gemstone shows different colors when viewed from different directions under polarized light?

a) Pleochroism

b) Iridescence

c) Aventurescence

d) Dispersion

34. Which gemstone is known for its billowy, bluish light effect?

a) Labradorite

b) Moonstone

c) Opal

d) Sunstone

35. What is the term for the phenomenon where light separates into its component colors as it passes through a gemstone?

a) Dispersion

b) Refraction

c) Reflection

d) Polarization

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