UPSC NDA-2

31. Light year is a measure of

Light year is a measure of

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time
distance
total amount of light falling on the Earth in a year
average intensity of light falling on the Earth in a year
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A light-year is defined as the distance that light travels in vacuum in one Julian year (365.25 days). Because light travels at a finite, constant speed in vacuum, the distance it covers over a fixed period of time is a specific value. Therefore, a light-year is a unit used to measure distances, particularly in astronomy, for vast interstellar and intergalactic scales.
– A light-year is the distance light travels in one year.
– It is a unit of distance.
– Used for measuring large distances in astronomy.
The speed of light in vacuum is approximately 299,792,458 meters per second. One light-year is approximately 9.461 trillion kilometers (9.461 × 10¹² km) or 5.879 trillion miles (5.879 × 10¹² miles). Other units of astronomical distance include the astronomical unit (AU) and the parsec (pc).

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32. If some object is weighed when submerged in water, what will happen to

If some object is weighed when submerged in water, what will happen to its weight compared to its weight in air ?

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Increase
Decrease
Remain exactly the same
Increase or decrease cannot be predicted
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UPSC NDA-2 – 2017
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When an object is submerged in water, it experiences an upward force exerted by the water, known as the buoyant force. This buoyant force opposes the object’s weight. The apparent weight of the object when submerged is equal to its true weight (weight in air) minus the buoyant force. Since the buoyant force is a positive value for any object submerged in a fluid, the apparent weight will always be less than the weight in air. Therefore, the weight of the object appears to decrease when submerged in water.
– Buoyant force is an upward force exerted by a fluid on a submerged object.
– Apparent weight = True weight – Buoyant force.
– Buoyancy causes the apparent weight to be less than the weight in air.
Archimedes’ principle states that the buoyant force on an object submerged in a fluid is equal to the weight of the fluid displaced by the object. The magnitude of the decrease in apparent weight is exactly equal to this buoyant force.

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33. Concave mirror is used in headlights of vehicles, because it

Concave mirror is used in headlights of vehicles, because it

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focuses light from the bulb onto nearby vehicles
sends parallel rays
fits well into the shape of the headlight
is cheaper than other mirrors
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UPSC NDA-2 – 2017
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A concave mirror is used in vehicle headlights because, when the light source (bulb) is placed at or near its focal point, it reflects the light rays as a nearly parallel beam. This parallel beam effectively projects the light forward, illuminating the road ahead.
Concave mirrors are used as reflectors in headlights to create a focused, parallel beam of light by placing the light source at or near the mirror’s focal point.
Other options are incorrect: A concave mirror reflects light forward, not onto nearby vehicles in a focused way; while shape fitting and cost are practical considerations, they are not the primary *optical* reason for choosing a concave mirror. Parabolic reflectors, a specific type of concave mirror, are commonly used in headlights to produce a highly parallel beam.

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34. Water boils at a lower temperature at high altitudes, because

Water boils at a lower temperature at high altitudes, because

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the air pressure is less
outside temperature is less
latent heat is less
None of the above
This question was previously asked in
UPSC NDA-2 – 2017
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Water boils at a lower temperature at high altitudes because the atmospheric pressure is lower. Boiling occurs when the vapor pressure of the liquid equals the surrounding atmospheric pressure. With lower external pressure, a lower temperature is needed for water’s vapor pressure to reach that level.
Boiling point is the temperature at which the vapor pressure of a liquid equals the ambient atmospheric pressure. Pressure decreases with increasing altitude, leading to a lower boiling point.
At sea level, the boiling point of water is 100°C (212°F) at standard atmospheric pressure. At significantly higher altitudes, such as in mountainous regions, the boiling point can be several degrees lower. For example, at an altitude of 5,000 feet (approx 1500m), water boils at about 95°C (203°F). This is why cooking times often need to be adjusted at high altitudes.

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35. Who among the following shared the Nobel Prize in 1962 along with Fran

Who among the following shared the Nobel Prize in 1962 along with Francis Crick and James Watson for their discoveries concerning the molecular structure of nucleic acids ?

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Erwin Chargaff
Maurice Hugh Frederick Wilkins
Rosalind Franklin
Phoebus Levene
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The Nobel Prize in Physiology or Medicine in 1962 was awarded jointly to James Watson, Francis Crick, and Maurice Hugh Frederick Wilkins for their discoveries concerning the molecular structure of nucleic acids (specifically DNA).
The discovery of the double helix structure of DNA by Watson, Crick, and Wilkins, significantly aided by the X-ray diffraction work of Rosalind Franklin (who was not awarded as the prize is not posthumous), was a landmark achievement in molecular biology.
– Erwin Chargaff is known for Chargaff’s rules, which state that in DNA, the amount of adenine (A) is approximately equal to the amount of thymine (T), and the amount of guanine (G) is approximately equal to the amount of cytosine (C). His work was important for Watson and Crick but he did not share the Nobel Prize for this discovery.
– Rosalind Franklin’s X-ray diffraction images (particularly Photo 51) were critical evidence used by Watson and Crick to determine the structure of DNA.
– Phoebus Levene is known for his work on the structure of nucleotides and nucleic acids in the early 20th century, including identifying the components of DNA (phosphate, sugar, base).

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36. Which one of the following microbes causes acidification and curding o

Which one of the following microbes causes acidification and curding of milk ?

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Lactic Acid Bacillus
Clostridium botulinum
Vibrio cholerae
Saccharomyces cerevisiae
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Acidification and curding of milk are caused by Lactic Acid Bacillus (or more generally, Lactic Acid Bacteria, LAB). These microbes ferment lactose (milk sugar) into lactic acid, which lowers the pH, causing the milk proteins (casein) to coagulate and curdle.
Lactic Acid Bacteria (LAB), including various species of *Lactobacillus*, *Streptococcus*, and *Lactococcus*, are responsible for the fermentation process that leads to the production of yogurt, cheese, and other fermented milk products.
– *Clostridium botulinum* is a bacterium that produces a potent neurotoxin causing botulism, often associated with improperly canned foods.
– *Vibrio cholerae* is a bacterium that causes cholera, a severe diarrheal disease, typically transmitted through contaminated water.
– *Saccharomyces cerevisiae* is a yeast commonly known as baker’s yeast or brewer’s yeast, used in baking (carbon dioxide production) and alcoholic fermentation.

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37. The term ‘Probiotic’ is applied to

The term ‘Probiotic’ is applied to

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Organic food
Antacid
Antibiotic
Live microbial food supplement
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The term ‘Probiotic’ is applied to live microbial food supplements. These are live microorganisms which, when administered in adequate amounts, confer a health benefit on the host.
Probiotics are beneficial microorganisms, usually bacteria or yeasts, which are consumed to improve the balance of the gut microbiota.
Probiotics are often found in fermented foods like yogurt, kefir, sauerkraut, kimchi, and supplements. They are distinct from prebiotics, which are non-digestible food ingredients that selectively stimulate the growth and activity of beneficial bacteria already in the colon.

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38. Which one of the following vitamins has a role in blood clotting ?

Which one of the following vitamins has a role in blood clotting ?

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Vitamin A
Vitamin D
Vitamin E
Vitamin K
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Vitamin K plays a crucial role in blood clotting. It is essential for the synthesis of several proteins, called coagulation factors, that are necessary for blood to clot properly.
Vitamin K is a fat-soluble vitamin vital for the synthesis of clotting factors (prothrombin, factors VII, IX, and X) in the liver.
– Vitamin A is important for vision, immune function, and cell growth.
– Vitamin D is primarily involved in calcium absorption and bone health.
– Vitamin E is an antioxidant that protects cells from damage.
– A deficiency in Vitamin K can lead to excessive bleeding.

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39. Which of the following statements about magnetite ore of iron is/are c

Which of the following statements about magnetite ore of iron is/are correct ?

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  • 1. It is known as black ore.
  • 2. It contains 60% to 70% of pure iron.
  • 3. It possesses magnetic properties.

Select the correct answer using the codes given below :

1 only
2 and 3 only
1 and 3 only
1, 2 and 3
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UPSC NDA-2 – 2017
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All three statements regarding magnetite ore of iron are correct. Magnetite is known as black ore, it has a high iron content ranging typically from 60% to 70% in good quality ores, and it possesses strong magnetic properties.
Magnetite (Fe3O4) is one of the main iron ores and is characterized by its dark color and magnetic properties, often being the highest quality iron ore due to its high iron content.
– Hematite (Fe2O3) is another major iron ore, typically reddish-brown and not magnetic. It usually has a lower iron content than high-grade magnetite.
– Magnetite is a ferrimagnetic mineral, meaning it is strongly attracted to magnets and can even become a permanent magnet itself (lodestone).

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40. Which set of the following biosphere reserves in India is included in

Which set of the following biosphere reserves in India is included in the World Network of Biosphere Reserves ?

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Gulf of Mannar, Nokrek, Panchmarhi and Simlipal
Gulf of Mannar, Kanchanjunga, Nokrek and Seshachalam
Nilgiri, Nokrek, Panchmarhi and Panna
Nilgiri, Nokrek, Panchmarhi and Seshachalam
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The set containing Gulf of Mannar, Nokrek, Panchmarhi, and Simlipal includes four Biosphere Reserves in India that are recognized and included in the UNESCO World Network of Biosphere Reserves.
India has designated Biosphere Reserves, and a subset of these are recognized by UNESCO and included in the World Network of Biosphere Reserves under the Man and the Biosphere (MAB) Programme.
As of late 2023, India has 12 Biosphere Reserves included in the World Network: Nilgiri, Gulf of Mannar, Sundarbans, Nanda Devi, Nokrek, Pachmarhi, Similipal, Achanakmar-Amarkantak, Great Nicobar, Agasthyamalai, Khangchendzonga, and Panna. Option A contains four reserves (Gulf of Mannar, Nokrek, Panchmarhi, Simlipal) which are all on this list. Option C also contains four reserves (Nilgiri, Nokrek, Panchmarhi, Panna) which are also on this list. However, given the context of UPSC questions and potential date of formulation, sets of sites included earlier are often preferred if multiple correct sets exist. Gulf of Mannar (2001), Nokrek (2009), Panchmarhi (2009), and Simlipal (2009) were all listed by 2009. Nilgiri (2000), Nokrek (2009), Panchmarhi (2009), but Panna was added much later (2020). Assuming the question predates the most recent additions, option A is the most likely intended correct answer. Seshachalam is a Biosphere Reserve designated by India but not included in the UNESCO World Network.

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