Contributed by Banarasi Tiwari, Retd. Principal, 295, Lath No. 2, Hanumanpur, At & P.O-Mughalsarai, District – Chandauli, Pin: 232101 (U.P.)

GemstonesBanarasi Tiwari

1. Most natural diamonds are formed in the lithospheric mantle of the earth at depths of:a) 90-120 km b) 100-130 kmc) 110-140 km d) 140-190 km

2. The red colour of a ruby is due to the element:a) Strontium b) Titaniumc) Chromium d) Lithium

3. Which of the following gemstones is the hardest?a) Topaz b) Emeraldc) Sapphire d) Opal

4. Nacre (i.e. the combination of aragonite and conchiolin) is the structural backbone of:a) Carnelian b) Ametrinec) Rhodonite d) Pearl

5. Emerald is a variety of the mineral:a) Feldspar b) Berylc) Olivine d) Corundum

6. The crystal structure of which gemstone is distinguished by its three-sided prisms?a) Turquoise b) Topazc) Tourmaline d) Tanzanite

7. In which gemstone, the presence of trisulphur radical anion imparts an intense blue colour?a) Lapis lazuli b) Onyxc) Amber d) Amethyst

8. The top quality fl awless and colourless (i.e. white) specimens of which mineral are also known as "Matura Diamond"?a) Aventurine b) Zirconc) Citrine d) Aquamarine

9. Sapphire and Ruby are the two gem varieties of:a) Garnet b) Berylc) Baryte d) Corundum

10. Topaz is a silicate mineral of Aluminium and:a) Fluorine b) Chlorinec) Bromine d) Iodine

11. Which gemstone is also called "Aventurine-feldspar"?a) Onyx b) Moonstonec) Sunstone d) Jade

TEST YOUR KNOWLEDGE

12. Moonstone is composed of two intermingled feldspar species – Orthoclase and:a) Albite b) Celsianc) Microcline d) Hyalophane

13. Peridot is a variety of Olivine (Forsterite), rich in:a) Barium b) Strontiumc) Magnesium d) Chromium

14. "Star sapphires" contain intersecting needle-like inclusions of:a) Glauberite b) Rutilec) Ekanite d) Calcite

15. A rare variety of natural sapphire, "Colour change sapphire" exhibits different colours in different lights, due to the presence of the impurities of:a) Cr & V b) Ba & Src) Cd & Bi d) Co & Ni

16. Which element is diffused into a sapphire under very high heat, to enhance its colour?a) Boron b) Berylliumc) Barium d) Bismuth

17. Which of the following has also been called "the most colourful mineral in the world"?a) Fluorite b) Malachitec) Tsilaisite d) Amazonite

18. Opal is a hydrated amorphous form of :a) Gypsum b) Silicac) Galena d) Spinel

19. A repeat unit of how many silica tetrahedra are present in the inosilicate (chain silicate) structure of Rhodonite:a) Three b) Fourc) Five d) Six

20. The fi rst laser was made with a rod of the synthetic: a) Emerald b) Rubyc) Topaz d) Zircon

Answers1) d 2) c 3) c 4) d 5) b 6) c 7) a 8) b 9) d 10) a 11) c 12) a 13) c 14) b 15) a 16) b 17) a 18) b 19) c 20) b.

62 | Science Reporter | January 2018

Electronics

Contributed by Sanjay Goswami, Yammuna G/13, A. Nagar, BARC, Mumbai-94

Sanjay Goswami

CM

1. Electronic oscillators are controlled crystal which are used:a) To generate more powerb) To keep the output constantc) To maintain the frequency constantd) To consume more power

2. What is the approximate characteristic voltage that develops across a red LED?a) 1.7 v b) 3.4 vc) 0.6 v d) 5 v

3. Transistors involve the use of:a) Semiconductor b) Rare Earth Elementc) Transition Elements d) None of these.

4. Which of the following is a semiconductor?a) Germanium (Ge) b) Copper (Cu)c) Selenium (Se) d) Both a & c

5. Transistors work like:a) CRO b) Thermionic Valvesc) TV d) Radar

6. A transistor consists of:a) Base and emitters b) Base and collectorsc) Collector and emitters d) Base, collector and emitter

7. In insulators, the valence band is:a) Filled with electrons b) Emptyc) Filled with protons d) Filled with neutrons

8. Which of the following has the shortest wavelengths?a) X-rays b) Radio wavesc) Gamma Rays d) IR waves

9. Connecting a lead from the negative to the positive of a battery will produce:a) A high resistance circuit b) A short circuitc) A low current path d) An open circuit

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e

10. At room temperature the conductivity of metals is of the order of:a) 106 – 108 per ohm per meterb) 104 – 105 per ohm per meterc) 1010 – 1012 per ohm per meterd) 1012 – 1014 per ohm per meter

11. The spacing between the two radio frequency carriers in TV transmission is:a) 1 MHz b) 2 MHzc) 4.5 MHz d) 6 MHz

12. The number of radio frequency carrier waves transmitted by TV transmission is:a) 1 b) 2c) 4 d) 6

13. At room temperature the conductivity of insulators is of the order of:a) 10-20 – 10-8 per ohm per meterb) 10-30 – 10-20 per ohm per meterc) 10-10 – 10-2 per ohm per meterd) 102 – 10-4 per ohm per meter

14. In insulators, the conduction band is:a) Filled with electrons b) Emptyc) Filled with protons d) Filled with neutrons

15. Capacitors are classifi ed according to the material used in their manufacturing process. Which one of the following is not a type of capacitor?

a) Electrolytic b) Tantalum c) Ceramic d) None of the above

16. An oscillator in principle is one ____________________ circuit.a) AC to DC converter b) Input voltage doublerc) DC to AC converter d) None of the above

Answers1) c 2) a 3) a 4) d 5) b 6) d 7) a 8) c 9) b 10) a 11) c 12) b 13) a 14) b 15) d 16) c

January 2018 | Science Reporter | 63