Concept Application and Fact for Prelims Day-42

This is the Day-42 questions of the CAF Revision plan for prelims. The questions are based on the syllabus as provided in the schedule. Aspirants are requested to go through the detailed CAF strategy to understand the need of the UPSC prelims and to prepare well for the same. Attempt the questions honestly. The link to key answers and explanations of this test is at the end of the questions. The maximum time to attempt the 15 questions is 20 minutes.

Q.1) Which of the following is/are the example/examples of chemical change?

  1. Crystallization of sodium chloride
  2. Melting of ice
  3. Souring of milk

Select the correct answer using the code given below.

(a) 1 and 2 only

(b) 3 only

(c) 1, 2 and 3

(d) None

Q.2) Consider the following phenomena:

  1. Light is affected by gravity.
  2. The Universe is constantly expanding.
  3. Matter warps its surrounding space-time.

Which of the above is/are the prediction/predictions of Albert Einstein’s General Theory of Relativity, often discussed in media?

(a) 1 and 2 only

(b) 3 only

(c) 1 and 3 only

(d) 1, 2 and 3

Q.3) The tendency of a liquid drop to contract and occupy minimum area is due to:

(a) surface tension

(b) viscosity

(c) density

(d) vapour pressure

Q.4) The working principle of a washing machine is:

(a) centrifugation

(b) dialysis

(c) reverse osmosis

(d) diffusion

Q.5) For which one of the following is capillarity not the reason?

(a) Blotting of ink

(b) Rising of underground water

(c) Spread a water drop on a cotton cloth

(d) Rising of water from the roots of a plant to its foliage

Q.6) Consider the following

Assertion (A) : An iron ball floats on mercury but gets immersed in water.

Reason (R) : The specific gravity of iron is more than that of mercury.


(a) Both A and R are true and R is the correct explanation of A

(b) Both A and R are true but R is not a correct explanation of A

(c) A is true but R is false

(d) A is false but R is true

Q.7) Consider the following statements:

A 4-wheel vehicle moving in a sharp circular path at high speed will :

  1. overturn about its outer wheels
  2. overturn about its inner wheels
  3. skid outwards
  4. skid inwards

Which of these statements are correct?

(a) 1 and 3

(c) 2 and 3

(b) 2 and 4

(d) 1 and 4

Q.8) Consider the following statements:

If there were no phenomenon of capillarity

  1. it would be difficult to use a kerosene lamp
  2. one would not be able to use a straw to consume a soft drink
  3. the blotting paper would fail to function
  4. the big trees that we see around would not have grown on the Earth

Which of the statements given above are correct?

(a) 1, 2 and 3 only

(b) 1, 3 and 4 only

(c) 2 and 4 only

(d) 1, 2, 3 and 4

Q.9) Ball bearings are used in bicycles, cars, etc., because

(a) the actual area of contact between the wheel and axle is increased

(b) the effective area of contact between the wheel and axle is increased

(c) the effective area of contact between the wheel and axle is reduced

(d) None of the above statements is correct

Q.10) The surface of a lake is frozen in severe winter, but the water at its bottom is still liquid. What is the reason?

(a) Ice is a bad conductor of heat.

(b) Since the surface of the lake is at the same temperature as the air, no heat is lost.

(c) The density of water is maximum at 4-degree C.

(d) None of the statements (a), (b) and (c) given is correct.

Q.11) Optical fibre works on the principle of:

(a) total internal reflection

(b) refraction

(c) scattering

(d) interference

Q.12) Consider the following natural phenomena:

  1. Terrestrial heating
  2. Reflection of light
  3. Refraction of light
  4. Diffraction of light

Due to which of these phenomena is a mirage formed?

(a) 1 and 2

(b) 2, 3 and 4

(c) 1 and 3

 (d) 4 only

Q.13) Diffusion of light in the atmosphere takes place due to:

(a) carbon dioxide

(b) dust particles

(c) helium

(d) water vapours

Q.14) When a CD (compact disc used in audio and video systems) is seen in sunlight, rainbow like colours are seen. This can be explained on the basis of the phenomenon of:

(a) reflection and diffraction

(b) reflection and transmission

(c) diffraction and transmission

(d) refraction, diffraction and transmission

Q.15) Which one of the following types of waves are used in a night vision apparatus?

(a) Radio waves

(b) Microwaves

(c) Infra-red waves

(d) None of the above

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