UPSC 2021 Science & Technology Previous Year Questions

Question 1

Which one of the following is a reason why astronomical distances are measured in light-years?

Accepted Answer

Correct Option: D. Distances among stellar bodies do not change. | Gravity of stellar bodies does not change. | Light always travels in straight line. | Speed of light is always same.. Light-year is a distance unit based on the constant speed of light in vacuum, useful for expressing huge astronomical distances.

Question 2

'Triclosan', considered harmful when exposed to high levels for a long time, is most likely present in which of the following?

Accepted Answer

Correct Option: D. Food preservatives | Fruit-ripening substances | Reused plastic containers | Toiletries. Triclosan has been used as an antimicrobial ingredient in personal care products/toiletries such as soaps and toothpaste.

Question 3

With reference to street-lighting, how do sodium lamps differ from LED lamps? 1. Sodium lamps produce light in 360 degrees but it is not so in the case of LED lamps. 2. As street-lights, sodium lamps have longer life span than LED lamps. 3. The spectrum of visible light from sodium lamps is almost monochromatic while LED lamps offer significant color advantages in street-lighting. Select the correct answer using the code given below.

Accepted Answer

Correct Option: C. 3 only | 2 only | 1 and 3 only | 1, 2 and 3. Sodium lamps emit light broadly in all directions and have nearly monochromatic yellow light, whereas LEDs are directional and offer better color control. LEDs generally have longer life, so statement 2 is wrong.

Question 4

Water can dissolve more substances than any other liquid because

Accepted Answer

Correct Option: A. it is dipolar in nature | it is a good conductor of heat | it has high value of specific heat | it is an oxide of hydrogen. Water is an excellent solvent because its molecule is polar/dipolar, allowing it to interact with ions and polar molecules.

Question 5

Consider the following: 1. Bacteria 2. Fungi 3. Virus Which of the above can be cultured in artificial/synthetic medium?

Accepted Answer

Correct Option: A. 1 and 2 only | 2 and 3 only | 1 and 3 only | 1, 2 and 3. Bacteria and fungi can be cultured on artificial/synthetic media. Viruses require living host cells and cannot be cultured on non-living synthetic media alone.

Question 6

In a pressure cooker, the temperature at which the food is cooked depends mainly upon which of the following? 1. Area of the hole in the lid 2. Temperature of the flame 3. Weight of the lid Select the correct answer using the code given below.

Accepted Answer

Correct Option: C. 1 and 2 only | 2 and 3 only | 1 and 3 only | 1, 2 and 3. Pressure cooker cooking temperature depends on pressure, which is controlled by vent/hole area and the weight/pressure valve. Flame temperature mainly affects heating rate, not final pressure-controlled cooking temperature.

Question 7

Consider the following statements: 1. The Global Ocean Commission grants licences for seabed exploration and mining in international waters. 2. India has received licences for seabed mineral exploration in international waters. 3. Rare earth minerals are present on seafloor in international waters. Which of the statements given above are correct?

Accepted Answer

Correct Option: B. 1 and 2 only | 2 and 3 only | 1 and 3 only | 1, 2 and 3. The International Seabed Authority, not the Global Ocean Commission, grants seabed exploration licences. India has such licences, and rare earth/mineral resources occur on the international seabed.

Question 8

Who among the following was associated as Secretary with Hindu Female School which later came to be known as Bethune Female School?

Accepted Answer

Correct Option: C. Annie Besant | Debendranath Tagore | Ishwar Chandra Vidyasagar | Sarojini Naidu. Ishwar Chandra Vidyasagar was associated as secretary with Hindu Female School, later Bethune Female School.

Question 9

Which one of the following is a filter feeder?

Accepted Answer

Correct Option: C. Catfish | Octopus | Oyster | Pelican. Oysters are filter feeders, drawing water through their bodies and filtering plankton/particles.

UPSC 2021 Science & Technology PYQs with Answers