1.

The ‘leniency plus’ scheme seen in news pertains to

(a) The Competition Commission of India

(b) Securities and Exchange Board of India

(c) Central Board of Direct Taxes

(d) Reserve Bank of India

2.

Which of the following gives quantum computers parallelism?

(a) Entanglement

(b) Superposition

(c) Decoherence

(d) Interference  

3.

Consider the following statements:

1. Nuclear reactors have just a few percent fissile material in them and bombs have more than 90 percent.

2. In a nuclear reactor, the reaction is controlled, while in nuclear bombs, the reaction is uncontrolled.

3. In a nuclear reactor, all operating reactors are ‘critical’, while there is no question of ‘criticality’ in case of a nuclear bomb.

4. Nuclear reactors use moderators, while nuclear bombs do not use them.

Which of the above statements about operational principles of a nuclear reactor and a nuclear bomb are correct?.

(a) 1, 2 and 4 only

(b) 2, 3 and 4 only

(c) 1 and 3 only

(d) 1, 2, 3 and 4 only

4.

Consider the following statements w.r.t. cosmic inflation.

1. It indicates that the universe expanded at many times the speed of light a fraction of a second just after the Big Bang.

2. Primordial gravitational waves provide evidence of cosmic inflation.

(a) Only 1 is true

(b) Only 2 is true

(c) Both 1 and 2 are true

(d) Neither 1 nor 2 is true

5.

A boy is whirling a stone tied with a string in a horizontal circular path. If the string breaks, the stone

(a) will continue to move in the circular path

(b) will move along a straight line towards the centre of the circular path

(c) will move along a straight line tangential to the circular path

(d) will move along a straight line perpendicular to the circular path away from the boy

6.

TADOX Technology is connected with

(a) Levitating trains

(b) Super computers

(c) Waste water treatment

(d) Stem Cells

7.

James Chadwick discovered the

(a) Neutron 

(b) Neutrino

(c) Positron

(d) Antiproton

8.

What is homogenised milk that we buy daily in packets?

(a) Milk in which a little sodium carbonate is added.

(b) Milk in which bad fat is removed and good fat is added. 

(c) Milk in which fat particles are broken down. 

(d) Milk in which a whey is added by removing fats.

9.

Which of the following is/are true w.r.t. Galactic Cosmic Rays (GCRs)?

1. They originate primarily in solar flares.

2. Their major composition is hydrogen.

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

10.

Mangalajodi, India''s largest wintering ground for waterbirds is in

(a) Bihar

(b) Tamilnadu

(c) Kerala

(d) Odisha

11.

Which one of the following statements is incorrect? 

(a) Calcium Oxychloride is used as a bleaching agent.

(b) Calcium carbonate is an ingredient of toothpaste. 

(c) Bordeaux mixture consists of sodium sulphate and lime.

(d) Carbolic Acid is used as a disinfectant.

12.

Consider the following statements:

In a nuclear reactor, self-sustained chain reaction is possible, because:

1. more neutrons are released in each of the fission reactions.

2. the neutrons immediately take part in the fission process.

3. the fast neutrons are slowed down by graphite.

4. every neutron released in the fission reaction initiates further fission.

Which of these statements are correct?

(a) 1, 2 and 3

(b) 1 and 3

(c) 2 and 4

(d) 2, 3 and 4

13.

Which of the following is incorrect?.

(a) Benadryl - antihistamine

(b) Monosodium glutamate – food steriliser

(c) Hydrogen peroxide - wound dressing

(d) Zinc carbonate – itch reliever

14.

1. Georgia shares its borders with Azerbaijan, Armenia, Russia and Turkey.

2. Georgia is connected to the Caspian Sea.

(a) Only 1 is true

(b) Only 2 is true

(c) 1 & 2 are true

(d) Neither (1) nor (2) is true

15.

Which of the following is/are true w.r.t. RDX?

1. Chemically it is Cyclonite.

2. It is made by mixing nitric acid and hexamine.

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

16.

What is “Kiss of death” ?

(a) A flower with toxic smell of cyanide

(b) Protein named ubiquitin

(c) A mushroom in Guna Caves of Kodaikanal

(d) A neurotransmitter in brain that controls vital functions of the body

17.

With reference to the Accretion disks, consider the following statements. 

1. They are rings of gas and dust around black holes. 

2. They do not emit light.  

Which of these statements are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

18.

Why is nitrogen-9 special?

1. It is an allotrope are characterised by seven protons and two neutrons – which is an unusually high proton-to-neutron ratio.

2. It is highly stable.

(a) Only 1 is true.

(b) Only 2 is true.

(c) 1 & 2 are true

(d) Neither 1 nor 2 is true

19.

Which of the following is/are true w.r.t. Superfluid helium?

1. Superfluid helium has the highest viscosity.

2. Liquid helium is used as a coolant in large superconducting magnets.

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

20.

If a major solar storm (solar flare) reaches the Earth, which of the following are the possible effects on the Earth?

1.  GPS and navigation systems could fail.

2.  Tsunamis could occur at equatorial regions.

3.  Power grids could be damaged.

4.  Intense auroras could occur over much of the Earth.

5.  Forest fires could take place over much of the planet.

6.  Orbits of the satellites could be disturbed.

7.  Shortwave radio communication of the aircraft flying over polar regions could be interrupted.

Select the correct answer using the code given below:

(a) 1, 2, 4 and 5 only

(b) 2, 3, 5, 6 and 7 only

(c) 1, 3, 4, 6 and 7 only

(d) 1, 2, 3, 4, 5, 6 and 7

21.

Correct pair (is) are

1. Xenon - Stranger Gas

2. Nitric oxide - Laughing gas

3. Boric acid – Carrom Powder

(a) 1, 2 and 3

(b) 1 and 3 only

(c) 1 and 2 only

(d) 3 only

22.

Two wires have their lengths, diameters and resistivities all in the ratio of 1: 2. If the resistance of the thinner wire is 5 ohm, the resistance of the thicker wire is

(a) 5 ohm

(b) 10 ohm

(c) 20 ohm

(d) 40 ohm

23.

1. methane

2. hydrogen sulfide

3. carbon monoxide

4. carbon dioxide

Neurotoxic gases include

(a) 1 and 2

(b) 1 and 3

(c) 1, 3 and 4

(d) 1, 2, 3 and 4

24.

1. Calcium Carbide is used for artificial ripening of green fruits because it produces auxins.

2. Pyrene is used as a fire extinguisher because it contains carbon tetra-chloride.

Which of the above statements is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2  

(d) Neither 1 nor 2

25.

Which of the following is/are true?.

I. An Astronomical Unit is roughly 15 crore km.

II. An attosecond is one trillionth of a second.

III. One parsec is greater than one light year.

Codes:

(a) Only II

(b) Only I and II

(c) Only II and III

(d) I and III 

1.

https://www.thehindubusinessline.com/multimedia/audio/leniency-plus-ccis-new-weapon-in-the-battle-against-cartels/article67480297.ece 

https://www.thehindubusinessline.com/opinion/editorial/ccis-leniency-plus-will-hopefully-help-against-cartelisation/article67878776.ece

a  

2.

https://indianexpress.com/article/explained/explained-sci-tech/quantum-computers-and-india-8575969/

Principle of Quantum computing:

• Every quantum state can be represented as a sum of two or more other distinct states. 

• This superposition of qubits gives quantum computers parallelism, allowing them to process millions of operations simultaneously. 

• Quantum entanglement occurs when two systems link so closely that knowledge about one gives the immediate knowledge about the other, no matter how far they are.  

• Quantum entanglement allows quantum computers to solve complex problems faster. 

• Decoherence is the loss of the quantum state in a qubit. 

• Environmental factors like radiation can cause the quantum state of the qubits to collapse. 

B   

3.

https://www.syfy.com/syfy-wire/whats-the-difference-between-atomic-hydrogen-nuclear-bombs

https://www.energy.gov/ne/articles/beyond-oppenheimer-how-nuclear-weapons-and-nuclear-reactors-are-different#:~:text=Reactors%20and%20bombs%20use%20different%20fuel.&text=Commercial%20nuclear%20power%20plants%20use,tubes%20to%20make%20fuel%20rods.

D  

4.

It was first hypothesized by American physicist Alan Guth. The scientists from the Background Imaging of Cosmic Extragalactic Polarization 2 (BICEP2) found out the primordial gravitational waves, the first direct evidence of cosmic inflation theory. The data represent the first images of gravitational waves, or ripples in space-time. Thesewaves have been described as the “first tremors of the Big Bang”.

https://www.thehindu.com/sci-tech/science/multiverse-physics-theories-cosmic-inflation-explained/article67782934.ece

C 

5.

) If the string breaks, the force that was causing it to move along a circular path, i.e., centripetal force is no longer there, so the stone will move along a straight line tangential to the circular path.

C 

6.

https://www.thehindubusinessline.com/economy/teri-unveils-new-tech-to-ensure-zero-liquid-discharge-by-industrial-wastewater/article67903556.ece

C  

7.

https://www.thehindu.com/sci-tech/science/pulsar-glitch-rotation-neutron-degeneracy-superfluid-explained/article67531899.ece

https://www.vedantu.com/physics/antiparticle

A 

8.

Toned milk is created by adjusting the fat content by adding water-soluble non-fat milk solids. This process results in a beverage with a reduced fat percentage, typically around 3%. The primary goal of toning milk is to strike a balance between the richness of full-fat milk and the lower fat content of skim milk. The process retains a significant portion of the essential nutrients found in whole milk, making it a nutritious option.

C  

9.

https://www.thehindu.com/sci-tech/science/amaterasu-cosmic-ray-physics-explained/article67690711.ece

B  

10.

Mangalajodi is a village located on the northern edge of Chilika Lake in Odisha, not Andhra Pradesh. Mangalajodi is indeed recognised as globally important for the conservation of bird population. It is a wetland of national importance and has been recognized as an Important Bird Area (IBA) by BirdLife International. The area is home to a wide variety of migratory birds, including the endangered and rare species. The wetland provides an ideal habitat for birds to roost, nest, and feed.

D  

11.

https://www.vedantu.com/question-answer/bleaching-powder-is-used-for-disinfecting-class-11-chemistry-cbse-5f7502b67356f10c24fdfef3

https://www.vedantu.com/chemistry/carbolic-acid

The principal ingredients of a toothpaste, calcium carbonate and calcium hydrogen phosphate, remove the dirt on teeth. These ingredients also polish the teeth.

Bordeaux mixture—a combination of copper sulfate, lime, and water—is an effective fungicide and bactericide that has been used for decades to control diseases of fruit and nut trees, vine fruits, and ornamental plants.

C 

12.

A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. The most common use of nuclear reactors is for the generation of electrical power and for the power in some ships. In every fission reaction in which uranium nuclei splits up to give smaller nuclei three more neutrons are produced which further results into splitting of heavy uranium nuclei and a greater number of neutrons will be produced. Thus, statement, 1 and 2 are correct. In nuclear reactor all the neutrons produced can not take part in fission reaction, else reaction can turn out extremely violent. Thus, graphite rods are used as a control rod to slow down the speed of fast-moving neutrons. Thus, statement 3 is also correct.

A

13.

Hydrogen peroxide is used for hair bleaching and for oxidation in permanent hair dyes and in oral hygiene products such as mouth-rinses and dentifrices as well as in tooth bleaching products. Hydrogen peroxide is a mild antiseptic used on the skin to prevent infection of minor cuts, scrapes, and burns.

 https://indianexpress.com/article/lifestyle/food-wine/what-is-ajinomoto-msg-impact-your-body-risk-food-8993166/

The active ingredient in BENADRYL is an antihistamine called diphenhydramine HCl. Antihistamines are used for relief from symptoms related to hay fever, upper respiratory allergy, or cold symptoms. Antihistamines are a class of drugs that block histamine from binding to H1 receptors in the body.

Uses of Zinc Carbonate

·    It is an inorganic salt and is commonly used as a catalyst in organic synthesis reactions.

·    Due to its fungicide and antiseptic properties. It is used in a wide range of products such as bath, make-up, personal cleanliness, shaving, oral care, and skin & hair care products. Zinc carbonate is a white crystalline powder that occurs naturally as granular or earthy masses. It is referred to as smithsonite or calamine or zinc spar.

·    It is also used in animal feed additives. Lack of zinc carbonate can restrict the animal’s growth because it has an important contribution for the development of bone.

B 

14.

Georgia is a transcontinental country located at the intersection of Eastern Europe and West Asia.  It is located at the eastern end of the Black Sea and southern flanks of Greater Caucasus Mountains.

A

15.

RDX is an explosive solid, also known as Cyclonite, hexogen, and T-4.

Its chemical formula is C3H6N6O6 and it has a velocity of 8750 m/sec, making it more powerful than TNT.

It is a colorless solid that is made by mixing nitric acid and hexamine.

During the Second World War, it was often used due to its high explosive properties.

C  

16.

Aaron Ciechanover, Avram Hershko and Irwin Rose have been awarded the Nobel Prize in Chemistry 2004 for “...helping to understand how the human body gives the ''kiss of death'' to rogue proteins to defend itself from diseases like cancer”. These scientists—the former two from Israel, the latter from the US — discovered ubiquitin-mediated protein degradation. Knowledge of ubiquitin-mediated protein degradation offers an opportunity to develop drugs against cervical cancer, cystic fibrosis and other diseases.’

The "kiss of death" for proteins is called ubiquitin. It is itself a protein, a tiny one consisting of only 76 amino acids. It acts as the "kiss of death" for other proteins. In the normal course of events, proteins need to be broken down and their parts recycled. This is done, it turns out, by tagging proteins with ubiquitin, a process called ubiquination. Ubiquitin is the signal to the cell''s transport machinery to ferry a protein to the proteasome, a barrel-shaped chamber floating in the cell cytoplasm. Proteasomes then slice the protein into bits that are recycled into new proteins. Antagonizing this process are enzymes that remove ubiquitin from proteins and prevent them being degraded.

https://indianexpress.com/article/lifestyle/health/mechanism-regulating-ptsd-female-brains-found-8620014/

https://indianexpress.com/article/lifestyle/health/scientists-new-approach-medicines-against-flu-8466079/

B     

17.

They emit light, including X-rays.  

https://www.thehindu.com/sci-tech/science/the-brightest-object-in-the-universe-is-a-black-hole-that-eats-a-star-a-day/article67866519.ece

Black Holes

• Black holes are mysterious cosmic objects, often misunderstood. They are not actual holes but incredibly dense concentrations of matter.
• It is typically formed during supernova explosions.
• A black hole’s event horizon, just beneath its surface, has such intense gravity that nothing, not even light, can escape it.
• This event horizon contains all the matter that makes up the black hole.

Finding Black Holes

• Black holes are invisible to telescopes because they do not emit or reflect light. Scientists detect and study them through various means:
• Accretion disks: Rings of gas and dust around black holes emit light, including X-rays.
• Stellar orbits: Intense gravity from supermassive black holes causes stars to orbit them uniquely.
• Gravitational waves: Massive objects create ripples in space-time when they accelerate, which scientists can detect.
• Gravitational lensing: Black holes can bend and distort light from distant objects, revealing their presence.

Determining Minimum Mass

• By studying the orbit of the visible star, astronomers can determine the minimum mass of the black hole.
• An example is the X-ray source in the constellation Cygnus, known as Cygnus X1, which is estimated to be about six times the mass of the Sun.
• This estimation rules out the possibility of it being a dwarf star or a neutron star, confirming that it is a black hole.

Key Black Hole Facts

• Closest: The nearest known black hole, 1A 06200-00, is 3,000 light-years away.
• Farthest: In the galaxy, QSO J0313-1806, is about 13 billion light-years away.
• Biggest: TON 618, is 66 billion times the mass of the Sun.
• Smallest: The lightest-known black hole is only 3.8 times the Sun’s mass and is paired with a star.
• Spaghettification: The process by which (in some theories) an object would be stretched and ripped apart by gravitational forces on falling into a black hole.
• It’s squeezed horizontally and stretched vertically, resembling a noodle.
• Spin: All black holes spin, with the fastest-known, GRS 1915+105, rotating over 1,000 times per second.
• Particle accelerators: Monster black holes at galaxy centers can launch particles to nearly light speed.
• Not so rare: Most Milky Way-sized galaxies have supermassive black holes at their centers, such as Sagittarius A*, which is 4 million times the mass of the Sun.

A   

18.

It is an isotope are characterised by seven protons and two neutrons – which is an unusually high proton-to-neutron ratio.

https://www.thehindu.com/sci-tech/science/nitrogen-9-nucleus-stability-challenge-nuclear-structure/article67550743.ece

A   

19.

Superfluid helium is a liquid that has zero viscosity.

https://www.thehindu.com/sci-tech/health/first-india-made-mri-scanner-by-bengaluru-based-voxelgrids-innovations-to-be-launched-for-clinical-work-in-october-will-potentially-cut-the-cost-of-scanning-by-30/article67187471.ece#:~:text=These%20and%20other%20innovations%20characterise,of%20Higher%20Medical%20Sciences%2C%20Bengaluru.

https://www.thehindu.com/sci-tech/science/kulhad-chai-bubbles-viscosity-superfluid-helium/article67629720.ece

B

20.

https://www.thehindu.com/sci-tech/science/sun-observing-spacecraft-sheds-light-on-the-solar-winds-origin/article67234433.ece

Geomagnetic storms

·      A geomagnetic storm is a major disturbance of Earth’s magnetosphere that occurs when there is a very efficient exchange of energy from the solar wind into the space environment surrounding Earth.

·      These storms result from variations in the solar wind that produces major changes in the currents, plasmas, and fields in Earth’s magnetosphere.

·      The solar wind conditions that are effective for creating geomagnetic storms:

o   Sustained (for several to many hours) periods of high-speed solar wind.

o   Southward directed solar wind magnetic field (opposite the direction of Earth’s field) at the dayside of the magnetosphere. This condition is effective for transferring energy from the solar wind into Earth’s magnetosphere.

o   High-speed solar wind stream (HSS).

·      The largest storms that result from these conditions are associated with solar coronal mass ejections (CMEs) where a billion tons or so of plasma from the sun arrives at Earth.

·      Storms also result in intense currents in the magnetosphere, changes in the radiation belts, and changes in the ionosphere, including heating the ionosphere and upper atmosphere region called the thermosphere.

Impacts of such storms:

·      Increase in the density in the upper atmosphere, causing extra drag on satellites in low-earth orbit.

·      Horizontal variations in the in the ionospheric density that can modify the path of radio signals and create errors in the positioning information provided by GPS.

·      Storms create beautiful aurora.

·      They also can disrupt navigation systems such as the Global Navigation Satellite System (GNSS).

·       They can create harmful geomagnetic induced currents (GICs) in the power grid and pipelines.

Magnetosphere

·      It is the region around a planet dominated by the planet’s magnetic field. Other planets in our solar system have magnetospheres, but Earth has the strongest one of all the rocky planets.

·      Earth’s magnetosphere is a vast, comet-shaped bubble, which shields our home planet from solar and cosmic particle radiation, as well as erosion of the atmosphere by the solar wind – the constant flow of charged particles streaming off the sun.

·      It is generated by the convective motion of charged, molten iron, far below the surface in Earth’s outer core.

·      Constant bombardment by the solar wind compresses the sun-facing side of our magnetic field. The sun-facing side, or dayside, extends a distance of about six to 10 times the radius of the Earth. The side of the magnetosphere facing away from the sun – the nightside – stretches out into an immense magnetotail, which fluctuates in length and can measure hundreds of Earth radii, far past the moon’s orbit at 60 Earth radii.

Ionosphere and Magnetosphere

·      The ionosphere is a region within the upper mesosphere and thermosphere where solar radiation and particles in the “solar wind” strip electrons from atoms in the atmosphere and create an electrically charged zone of ions. It is used to communicate long distances by radio. Radio waves bounce off the ionosphere in much the same way that light is reflected by a mirror. The ionosphere changes its position from day to night, rising in the night and lowering in the day. This is why radio signals from far off places can be detected at night, while only close by transmissions are detectable during the day.

·      The magnetosphere is Contained within the Earth’s thermosphere and is the region where the Earth’s magnetic field interacts with the charged particles coming from the Sun in the solar wind. These particles become trapped in the magnetic field of the Earth and circulate around the Earth following the Earth’s magnetic field. Large bombardments of these charged particles cause the auroras in the ionosphere as they follow the Earth’s magnetic field through the upper atmosphere towards the magnetic poles.

Van Allen radiation belts

·      The Van Allen radiation belt is a zone of energetic charged particles, most of which originate from the solar wind. The particles are captured by and held around a planet by that planet’s magnetic field. It surrounds Earth, containing a nearly impenetrable barrier that prevents the fastest, most energetic electrons from reaching Earth.

The outer belt is made up of billions of high-energy particles that originate from the Sun and become trapped in Earth’s magnetic field, an area known as the magnetosphere. The inner belt results from interactions of cosmic rays with Earth’s atmosphere.

C   

21.

Boric acid is a solid lubricant and is used to reduce friction. It is used as a lubricant to make motion smooter. In carrom boards, boric acid is used for smooth gliding of porous because H3BO3 molecules are loosely chemically bounded and hence soft and thus reduce friction.

Nitrous oxide (N2O), commonly known as laughing gas or happy gas, was first discovered in 1793 by the English scientist Joseph Priestly and has been used for more than 150 years. It has remained one of the most widely used anesthetics in both dental and medical applications. Nitrous oxide is small inorganic chemical molecule and may also be known as dinitrogen oxide or dinitrogen monoxide. It is a colorless and nonflammable gas with a slightly sweet odor. Nitrous oxide also has some illicit recreational uses and abuse potential. It is widely used in multiple nonmedical areas. Some of the nonmedical uses of nitrous oxide include the semiconductor industry, car racing, and food processing.

Xenon(Xe) gas is also known as stranger gas. It is called ''STRANGER GAS'' because the word ''XENON'' means ''STRANGE'' in Greek. It was discovered by William Ramsay and Morris Travers in 1898. It is more than 4.5 times heavier than air.

B   

22.

Resistance (R) of a length l, resistivity ρ and area of cross-section A is given by

For the two wires,

∴ R1 = R2 = 5 ohm
(∵ ρ1 : ρ2 = l1 : l2 = 1 : 2 and A1 : A2 = 1 : 4)

A  

23.

https://indianexpress.com/article/explained/explained-health/ludhiana-gas-leak-deaths-neurotoxins-explained-8585039/

Neurotoxic gases are poisonous substances that can directly affect the nervous system. They can disrupt or even kill neurons or nerve cells, which are essential for transmitting and processing signals in the brain and other parts of the nervous system. Examples of common neurotoxic gases include methane, hydrogen sulfide, carbon monoxide, and carbon dioxide. 

D   

24.

Calcium Carbide is used for artificial ripening of green fruits because it produces acetylene.  

-In the given question, we have to identify the correct gas which is responsible for the artificial ripening of the fruit.

-The hormones responsible for the growth and development of the plant is known as plant growth.

-There are many types of plant growth hormones such as gibberellins, cytokinin, ethylene and abscisic acid.

-Among all the hormones, ethylene is responsible for the faster ripening of the fruit because it helps in increasing the rate of respiration, change in colour, odour and taste.

-Here, ethylene is produced naturally by the plants but for the artificial ripening of fruit, we use acetylene gas.

-For the production of acetylene gas, calcium carbide is used. When it comes in contact with the moisture it yields calcium hydroxide as well as acetylene gas which works similar to the ethylene.

-The balanced chemical reaction is:

CaC2 + H2O → C2H2 + Ca(OH)2

-That''s why ethylene gas and acetylene gas are considered as ripening agents.

Fire Extinguishers, Building Materials & Glass

Different types of fire extinguishers generally used are:
Household fire extinguishers.
(a) Dry powder extinguishers.
(b) Baking soda, sulphuric acid-type fire extinguishers.

Foamite fire extinguishers.
Pyrene fire extinguishers

Household fire extinguishers:

Air containing about 16% of carbon dioxide does not support combustion. Carbon dioxide is, therefore, used for extinguishing fire.

(a) Dry powder fire extinguishers: These contain sand and baking soda which is thrown over burning fire where it is decomposed by heat and carbon dioxide is liberated.
As the percentage of carbon dioxide in air surrounding the burning object increases, the burning decreases. It is extinguished completely when the percentage of carbon dioxide in the surrounding air reaches 15%.

(b) Baking soda, sulphuric acid type fire extinguishers: It contains a bottle of sulphuric acid supported in a metallic container filled with strong baking soda solution. On striking the knob, the acid bottle breaks and carbon dioxide is liberated by the action of acid on baking soda. As more and more of carbon dioxide is produced, its percentage in air surrounding the burning object increases and brings the fire under control.

Foamite fire extinguishers

In this type of fire extinguisher, sulphuric acid is replaced by aluminium sulphate and licorice extract.

Pyrene fire extinguishers

Pyrene is a carbon tetra-chloride and its vapours do not catch fire, i.e., it is inflammable. It is, therefore, used as a fire extinguisher. When pyrene is thrown along with water on the burning object, carbon tetrachloride vapours surround the fire and thus cut-off the supply of air. The fire is thus extinguished. It is an ideal fire extinguisher for extinguishing fire is an electrical equipment.

Building Materials and Glass:
Portland Cement
Portland cement is in the form of finely divided grey powder composed of lime, alumina, silica and iron oxide. Small amounts of magnesia, sodium, potassium and sulphur are also present. Manufacturing of cement lies in mixing all its components thoroughly and then is heated to near fusion points, i.e., 1400°C. The clinker obtained is mixed with 2 to 3% gypsum and then finely pulverized.

Mortar: These are the mixtures of cement and sand and occasionally other fine aggregates. They are used for bonding in masonry and as surface covering also.

Concrete: It is mixture of cement, sand and coarse aggregates. The mixture is made into a solid mass. The size of the coarse aggregate varies with the purpose for which the concrete is required.

Reinforced Concrete: Reinforced concrete is an ordinary concrete, reinforced with steel rods or heavy wire mesh. Concrete is poured around steel rods or heavy wire mesh. On settling, the concrete adheres very strongly to the reinforcements. The reinforced concrete can withstand not only high tensile strength but also high compressive stresses.

Lime: Lime is calcium oxide which is used as mortar, plaster or insecticides in refractory bricks in metallurgy as flux, in paper as sizing material, in water softening and as a fertiliser for liming soil.

Plasters of Paris: Chemically it is a calcined gypsum. Plaster of paris is obtained from gypsum heating upto the temperature 120°C-160°C. Plaster of Paris finds its uses in decoration, dentists use it for making impressions for dentures, for making wall plasters, structural tiles, etc.

Glass
It is a ceramic material consisting of a uniformly dispersed mixture of silica, i.e. sand (75%), soda (20%), and lime (5%), often combined with such metallic oxides as those of calcium, lead, lithium, ceranium, etc., depending on the specific properties desired. The blend is heated to fusion temperature (about 700-800°C) and then gradually cooled (annealed) to a rigid, friable state, often referred to as vitreous. Technically glass is an amorphous, under-cooled liquid of extremely high viscosity which has all appearances of solid.

Types of Glasses
Glass ceramic: A devitrified or crystallized form of glass whose properties can be made to vary over a wide range. It has specific gravity of 2.5, thermal shock resistance 800°C.

Derivation: A standard glass formula to which a nucleating agent such as titania has been added, is melted, rolled into sheet and cooled. It is then heated to the temperature at which nucleation occurs.

Uses: Laboratory bench tops, architectural panels, restaurant heating and warming equipment, telescopic mirror.

Glass Fibre: These are special quality glass, having specific gravity 2.54 and softens above 815°C.

Uses: As thermal, caustic and electrical insulation, decorative and utility fabrics, table linen, fire-cord, as belt between tread and car case.

Glass Metallic:

Metal alloys having an amorphous atomic structure similar to that of silica glass, achieved by cooling of the molten alloy so rapidly that no crystalline structure is formed. Such alloys are said to be harder than their crystalline counterparts and are more resistant to corrosion.

Glass Optical: The optical glass is that glass which has definite optical characteristics so that it can be used in optical instruments.

The Glass have very low viscosity so that it becomes free from bubbles in molten condition. The material used for the batch is free from impurities like iron, etc. The optical glass takes up desired polish on grinding and polishing.

Safety Glass

Fig. Sealed safety glassIt is glass which on breaking does not allow its broken pieces to fly apart and causes injury to the people around.
There are two types of safety glasses:
(a) Laminated Safety Glass,
(b) Heat Tempered Glass 

In the laminated safety glass, two sheets of glass are pasted by means of plastic adhesives to two sides of plastic sheet, so the plastic sheet is sandwiched in between the two glass sheets.

The plastic and glass sheets are pressed together under heat to seal the edges. Then the glass is subjected to high temperatures and pressure in an autoclave so that the inner layers come into close contact. Then the edges of the combined sheets are sealed with a water resistant compound.

B 

25.

(d) I and III – PLEASE NOTE.

1 light minute is the distance light travels in a vacuum in one minute that is approximately 18 million kilometers.

A light-minute is 60 light-seconds, and so the average distance between Earth and the Sun is 8.317 light-minutes.

One light-year is equal to 525,960.00 light-minutes. Light-year is the distance light travels in one year. Light zips through interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion kilometers) per year.

1 light year is defined as the distance traveled by light in one year.

Speed of light c=3×108m/s

Number of seconds in 1 year t=1×365×24×60×60 seconds

∴ t=3.1536×107 seconds

Thus 1 light year =ct

Or 1 light year =3×108×3.1536×107=9.46×1015 m

An Astronomical Unit (AU) is the average distance between Earth and the Sun, which is about 93 million miles or 150 million kilometers. Astronomical units are usually used to measure distances within our Solar System.

The Moon is an average of 3,84,400 km away from Earth, that is approximately 0.0214 light minute away.

One parsec is 3.26 light years.

In 1838, the German astronomer Bessel measured the distance between Earth and binary star 61 Cygni as 10.3 light-years.

An attosecond is one quintillionth of a second.

https://www.news18.com/viral/did-you-know-how-unimaginably-long-1-light-year-is-8646333.html

https://www.thehindu.com/sci-tech/science/billion-light-year-wide-bubble-of-galaxies-discovered/article67285040.ece

https://www.thehindu.com/sci-tech/science/attophysics-new-tools-to-fathom-the-world-of-electrons-explained/article67393728.ece

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