1. Prologue
  2. Science: Physics
  3. Science: Chemistry
  4. Science: Biology


  • [T25] series contains 25 Mock MCQ for UPSC IAS/IPS Civil Service exam aspirants.
  • This particular article, gives you practice questions from science and technology theory.
  • Timelimit: 30 minutes.
  • 2 Marks for correct answer; -0.66 marks for wrong answer.

Science: Physics

Ray & Optics

Q. Infrared, visible and ultraviolet radiations/ light have different properties. Which one of the following statements related to these radiations/light is not correct? (CDS-2017-ii)

  1. The wavelength of infrared is more than that of ultraviolet radiation.
  2. The wavelength of ultraviolet is smaller than that of visible light.
  3. The photon energy of visible light is more than that of infrared light.
  4. The photon energy of ultraviolet is lesser than that of visible light.

HINT: NCERT Class12 Physics Ch.8:
wavelength of infrared vs UV light

  • Wavelength: Infrared: 10(-5) > Visible 10(-6) > Ultraviolet 10(-8) : meaning A and B are right.
  • Use the formula E = hv to obtain the photon energy, where v is the frequency of light. Since Frequency is inversely proportional to wavelength, therefore frequency wise and photon-energy wise: UV > Visible > Infra. So find the wrong statement between C and D accordingly.

Q. When the Sun is near the horizon during the morning or evening, it appears reddish. The phenomenon that is responsible for this observation is (CDS-2018-i)

  1. reflection of light
  2. refraction of light
  3. dispersion of light
  4. scattering of light

HINT: Light from the Sun near the horizon passes through thicker layers of air and larger distance in the earth’s atmosphere before reaching our eyes. Near the horizon, most of the blue light and shorter wavelengths are scattered away by the dust particles. Therefore, the light that reaches our eyes is of longer wavelengths. This gives rise to the reddish appearance of the Sun. Ref: NCERT Science Class10 Ch.11.

Q. Find incorrect statement(s) about Light and optics?

  1. Due to reflection of light, the sun is visible a little before the actual sunrise and until a little after the actual sunset due to refraction of light through the atmosphere
  2. Mirages are creates by Total internal reflection of light between layers of hot air.
  3. An observer can see a rainbow only when the sun is at 45 degrees to his shoulder.

Answer Codes:

  1. Only 1 and 2
  2. Only 2 and 3
  3. Only 2
  4. All of them

HINT: It’s not reflection but ‘refraction’ that creates advance sunrise and delayed sunset. An observer can therefore see a rainbow only when his back is towards the sun. Second statement is right- but here you’ve to identify the wrong statement. Read NCERT Class12 Physics ch.9 for more.

Q. Which of the following is suitable for making optical instruments? (CDS-2017-ii)

  1. Pyrex glass
  2. Soft glass
  3. Hard glass
  4. Flint glass


  1. Soft glass (soda glass) is brittle, cheapest and most commonly existing glasses- used for mirrors, window panes, electric bulbs, bottles.
  2. Hard Glass (Potash Glass) is hard to break and resistant to acid, hence used for laboratory apparatus for storing frog / flower specimens and hazardous chemicals.
  3. Pyrex (borosilicate) glass will not melt easily upon heating, hence useful in flasks, beakers and microwave oven utencils.
  4. Flint Glass – made up of – sodium, potassium and lead silicates- is used in making lenses of telescopes, microscopes, camera, prisms and idol objects of cultural importance.

Sound & Waves

Q. Sound waves cannot travel through a (CDS-2018-i)

  1. Copper wire placed in air
  2. Silver slab placed in air
  3. Glass prism placed in water
  4. Wooden hollow pipe loaded in a vacuum

HINT: Sound is a mechanical wave and needs a material medium like air, water, steel etc. for its propagation. It cannot travel through vacuum. Ref: NCERT Science Class9 ch.12

Q. Ultrasonic waves are produced by making use of (CDS-2017-ii)

  1. ferromagnetic material
  2. ferrimagnetic material
  3. piezoelectric material
  4. pyroelectrical material

HINT: NCERT Class11 Physics ch. 15 says that Ultrasonic waves in air are produced by vibrating quartz crystal. But it doesn’t use the specific term for this i.e. piezoelectric material.


Q. Two wires are made having same length l and area of cross-section A. Wire 1 is made of copper and wire 2 is made of aluminum. It is given that the electrical conductivity of copper is more than that of aluminum. In this context, which one of the following statements is correct? (CDS-2017-ii)

  1. The resistance of wire 1 will be higher than that of wire 2.
  2. The resistance of wire 2 will be higher than that of wire 1.
  3. The resistance of both the wires will be the same.
  4. If same current is flown through both the wires, the power dissipated both the wires will be  the same.

HINT: Conductivity and Resistance are inversely related so electrical resistance of Aluminum will be higher than Copper. Ref: NCERT Science Class10 Ch.12, Table 12.2 OR NCERT Class12 Physics Ch3.

Q. Working of safety fuses depends upon (CDS-2018-i)

  1. magnetic effect of the current
  2. chemical effect of the current
  3. magnitude of the current
  4. heating effect of the current

Select the correct answer using the code given below.

  1. 1, 2, 3 and 4
  2. 1, 2 and 3 only
  3. 3 and 4 only
  4. 4 only

HINT: The wire gets hot when an electric current passes through it. This is the heating effect of the electric current. Wires made from some special materials melt quickly and break when large electric currents are passed through them. These wires are used for making electric fuses If by accident the current exceeds this safe limit, the wires may become overheated and may cause fire. If a proper fuse is there in the circuit, it will blow off and break the circuit. Ref: NCERT Class7 Ch.14.

Q. Why is argon gas used along with tungsten wire in an electric bulb? (CDS-2018-i)

  1. To increase the life of the bulb
  2. To reduce the consumption of electricity
  3. To make the emitted light colored
  4. To reduce the cost of the bulb

HINT: Argon gas prolongs the life of filament by reducing the evaporation of tungsten.

Nuclear Energy & Misc

Q. Which of the following the fissile material is widely viewed as ‘Fuel of the future’?

  1. Uranium-238
  2. Uranium-235
  3. Thorium
  4. Plutonium

HINT: World resources of thorium are larger than those of uranium. Thorium, therefore is, widely viewed as the ‘fuel of the future’. Ref: India Yearbook 2018 Ch. 25
Q) Which of the following player is trying to increase the friction?

  1. Kabaddi players and Mud-wrestlers rubbing their hands with soil
  2. Gymnasts applying special type of power on their hands.
  3. Carrom Player sprinkling special type of powder on the carrom board.

Answer Codes:

  1. Only 1 and 2
  2. Only 2 and 3
  3. Only 3
  4. All of them

HINT: First two want to increase friction, to have better grip. Third will reduce the friction, but that’s not asked in the question. So, those ticking #3 – are making silly mistake, even though their science knowledge is correct. NCERT Class8 ch. 12 friction.

Q. Consider the following statements : (CDS-2017-ii)

  1. The chain reaction process is used in nuclear bombs to release a vast amount of energy, but in nuclear reactors, there is no chain reaction.
  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 ‘critically’ in case of a nuclear bomb.
  4. Nuclear reactors do not use moderators, while nuclear bombs use them.

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

  1. 1 and 3
  2. 2 and 3
  3. 4 only
  4. 1 and 4

HINT: NCERT Class12 Physics Ch.13:

  • Enrico Fermi (1939) first suggested that chain reaction can be either uncontrolled and rapid (as in a nuclear bomb) or controlled and steady (as in a nuclear reactor). The first leads to destruction while the latter can be harnessed to generate electric power. Hence #1 is wrong but 2 is right.
  • For K = 1, the operation of the reactor is said to be critical, which is what we wish it to be for steady power operation. If K becomes greater than one, the reaction rate and the reactor power increases exponentially. Unless the factor K is brought down very close to unity, the reactor will become supercritical and can even explode. Hence #3 is right.
  • In reactors, light nuclei called moderators are provided along with the fissionable nuclei for slowing down fast neutrons. The moderators commonly used are water, heavy water (D2O) and graphite. Therefore #4 is wrong.

Physics: Current Affairs

Q. 2017’s Nobel for Physics is given to Rainer Weiss, Barry C. Barish and Kip S. Thorne for their contribution in the field of:

  1. Neutrinos
  2. Gravitational-Waves and LIGO detector.
  3. Light-emitting diodes
  4. Large Hadron Collider and God particle.

HINT: 2013’s Nobel Physics was associated with Large Hadron Collider. 2017’s is for LIGO- the Laser Interferometer Gravitational-Wave Observatory, USA.

Q. Which one of the following planets was explored by Cassini Mission launched by NASA, which ended in September 2017 ? (CDS-2017-ii)

  1. Sun
  2. Neptune
  3. Saturn
  4. Jupiter

HINT: NASA launched Cassini in 1997. It had reached Saturn in 2004, and it was disintegrated in Saturn’s skies in 2017-September, in a carefully planed manner so that its debris don’t contaminate the planet. On a related topic, NASA’s Juno spacecraft entered the orbit of Jupiter in 2016, and UPSC had asked question about it in Mains-2017.

Science: Chemistry

Q. Consider the following constituent gases of the atmosphere: (CDS-2018-i)

  1. Argon
  2. Neon
  3. Helium
  4. Carbon dioxide

Which one of the following is the correct ascending sequence of the above gases, in terms of the volume percentage?

  1. 1-3-2-4
  2. 1-4-2-3
  3. 4-2-3-1
  4. 2-4-1-3

HINT: Observe the following table given in NCERT Geography Class11 Ch.8:
Argon Gas in atmosphere

Q. Tincture of iodine is an antiseptic for fresh wounds. It is a dilute solution of elemental iodine, which does not contain (CDS-2017-ii)

  1. water
  2. acetone
  3. alcohol

Answer Codes:

  1. Only 3
  2. Only 2 and 3
  3. Only 1 and 3
  4. All of them

HINT: Iodine is a powerful antiseptic. Its 2-3 per cent solution in alcohol-water mixture is known as tincture of iodine. It is applied on wounds.

Q. 2017’s Nobel for Chemistry is given to to Jacques Dubochet, Joachim Frank and Richard Henderso for their contribution in the field of:

  1. Structure and function of the ribosome
  2. Molecular machines
  3. Cryoelectron microscopy
  4. Fluorescence microscopy

HINT: Ribosome prize associated with Venkatara Ramakrishna aka Venki. (2009). 2017’s Chemistry Nobel is for cryo-electron microscopy- It helps detecting biomolecules in solution, thus helping biochemistry studies.

Q. Find incorrect statement(s) (Inspired from CDS-2017-ii)

  1. Emulsion is a mixture of two miscible liquids.
  2. Gemstone is an example of solid-solid colloid.
  3. Cheese, butter and jellies are examples of liquid-liquid colloids.
  4. All of the above.

HINT: if miscible liquids, then it’ll be a ‘solution.’ Emulsion is mixture of two immiscible or partially miscible liquids. Refer to this table from NCERT Class12 Chemistry ch.5 for better understanding of colloids, because that has been repeatedly asked in UPSC’s CDS and CAPF exams.

Q. Statement-I: Most of the medicines are colloidal in nature. Statement-II: Colloidal medicines have large surface area and are therefore easily assimilated in body. (Inspired from CDS-2017-ii)>

  1. Both the statements are individually true and Statement II is the correct explanation of Statement I.
  2. Both the statements are individually true but Statement II is not the correct explanation of Statement I
  3. Statement I is true but Statement II is false
  4. Statement I is false but Statement II is true.

HINT: Argyrol is a silver sol used as an eye lotion. Colloidal antimony is used in curing kalaazar. Colloidal gold is used for intramuscular injection. Milk of magnesia is used for stomach disorders. Both are right and II explains I. Refer to NCERT Class12 Chemistry ch.5 for more.

Q. Which one of the following radioactive substances enters/enter the human body through food chain and causes/cause many physiological disorders? (CDS-2017-ii)

  1. Strontium – 90
  2. Iodine – 131
  3. Cesium – 137
  4. All of the above

HINT: According to EPA: https://www.epa.gov/radiation/radionuclides

  • Cesium-137: Plants and vegetation growing in or nearby contaminated soil may take up small amounts of Cs-137 from the soil.
  • Iodine-131: if dairy animals consume grass contaminated with iodine, the radioactive iodine will be incorporated into their milk. Consequently, people can receive internal exposure from drinking the milk or eating dairy products made from contaminated milk.
  • Strontium-90: Plants or crops growing in or near contaminated soil may take up small amounts of Sr-90 from the soil. Animals may ingest Sr-90 when eating plants.

Science: Biology

Q. Which one of the following proteins gives lustrous shiny appearance to silk fibre? (CDS-2017-ii)

  1. Fibroin
  2. Sericin
  3. Collagen
  4. Nectin

HINT: Sericin’s main role is to envelop the fibroin. In presence of sericin the fibres are hard and tough and become soft and lustrous after its removal. So, guess which one of them is responsible?

Q. Match List-I with List-II and select the correct answer using the code given below the Lists : (CDS-2017-ii)

List-I (Cell Organelle)

  1. Mitochondria
  2. Chloroplast
  3. Ribosome
  4. Lysosomes
List-II (Functions)

  1. Photosynthesis
  2. Protein synthesis
  3. Intracellular digestion
  4. ATP formation

Code :

  1. A B C D: 3 1 2 4
  2. A B C D: 3 2 1 4
  3. A B C D: 4 1 2 3
  4. A B C D: 4 2 1 3

HINT: This is the minimum basics you must know! Ref: NCERT Science Class 9 ch.5p>

  1. Mitochondria are known as the powerhouses of the cell. The energy required for various chemical activities needed for life is released by mitochondria in the form of ATP (Adenosine triphopshate) molecules.
  2. The ribosomes, which are present in all active cells, are the sites of protein manufacture.
  3. Lysosomes help to keep the cell clean by digesting any foreign material, bacteria, food as well as worn-out cell organelles.

Q. Pearl is a hard object produced within the soft tissues of a mollusk. Which one of the following is the main constituent of pearl? (CDS-2017-ii)

  1. Calcium carbonate
  2. Calcium oxide
  3. Calcium nitrate
  4. Calcium sulphate

HINT: Calcium carbonate.

Q. The foul smell of urine of a healthy man having healthy food, when spilled on floor, is mainly due to the bacterial decomposition of (CDS-2017-ii)

  1. urea into sulphur dioxide
  2. sugar into carbon dioxide
  3. lipids into methane
  4. urea into ammonia

HINT: breakdown of urea into ammonia.

Q. Accumulation of which one of the following in the muscles of sprinters leads to cramp? (CDS-2018-i)

  1. Lactic acid
  2. Ethanol
  3. Pyruvic acid
  4. Glucose

HINT: When there is a lack of oxygen in our muscle cells, pyruvate is converted into lactic acid. This build-up of lactic acid in our muscles during sudden activity causes cramps. Ref: NCERT Science Class10 Ch.6, page 102.