General Science for UPSC

What you'll learn

Learn the core everyday-science ideas UPSC Prelims tests most: light, sound, heat, atoms, acids and bases, vitamins, and the human body.

This chapter has

General Science for UPSC — solved practice questions

8 UPSC Science & Technology questions with step-by-step solutions. Attempt each, then reveal the answer.

1. Q1medium

   The blue colour of the clear sky during the daytime is primarily due to which of the following phenomena?

   • ATotal internal reflection of sunlight
   • BRefraction of sunlight by water vapour
   • CReflection of sunlight by clouds
   • DScattering of sunlight by air molecules
   Show answer & solution

   Correct answer: (D) Scattering of sunlight by air molecules

   Shorter (blue) wavelengths of sunlight are scattered far more than longer wavelengths by the tiny gas molecules of the atmosphere (Rayleigh scattering), which makes the sky appear blue.

2. Q2medium

   Which one of the following physical quantities is a scalar quantity?

   • ASpeed
   • BVelocity
   • CDisplacement
   • DAcceleration
   Show answer & solution

   Correct answer: (A) Speed

   Speed has only magnitude and no direction, so it is a scalar; velocity, displacement and acceleration all have both magnitude and direction and are therefore vectors.

3. Q3medium

   Consider the following pairs of vitamins and the deficiency diseases they cause: 1. Vitamin A — Night blindness 2. Vitamin C — Scurvy 3. Vitamin D — Rickets How many of the pairs given above are correctly matched?

   • AOnly one pair
   • BOnly two pairs
   • CAll three pairs
   • DNone of the pairs
   Show answer & solution

   Correct answer: (C) All three pairs

   All three pairs are correct: Vitamin A deficiency causes night blindness, Vitamin C deficiency causes scurvy, and Vitamin D deficiency causes rickets in children.

4. Q4medium

   Which of the following gases is commonly known as 'laughing gas'?

   • ANitric oxide (NO)
   • BNitrous oxide (N2O)
   • CNitrogen dioxide (NO2)
   • DDinitrogen pentoxide (N2O5)
   Show answer & solution

   Correct answer: (B) Nitrous oxide (N2O)

   Nitrous oxide (N2O) is called laughing gas; it is used as a mild anaesthetic and produces a feeling of exhilaration when inhaled.

5. Q5medium

   Which of the following is the largest gland in the human body?

   • APancreas
   • BThyroid gland
   • CSalivary gland
   • DLiver
   Show answer & solution

   Correct answer: (D) Liver

   The liver is the largest gland as well as the largest internal organ in the human body; it secretes bile and performs numerous metabolic functions.

6. Q6hard

   Which of the following substances is basic (alkaline) in nature, having a pH value greater than 7?

   • ALemon juice
   • BVinegar
   • CMilk of magnesia
   • DCarbonated soft drink
   Show answer & solution

   Correct answer: (C) Milk of magnesia

   Milk of magnesia (magnesium hydroxide) is a base with a pH of about 10; lemon juice, vinegar and carbonated soft drinks are all acidic with pH values below 7.

7. Q7hard

   The central metal ion present in a molecule of chlorophyll is that of:

   • AIron
   • BMagnesium
   • CCalcium
   • DZinc
   Show answer & solution

   Correct answer: (B) Magnesium

   Chlorophyll contains magnesium at the centre of its porphyrin ring, whereas the analogous animal pigment haemoglobin contains iron.

8. Q8medium

   Which one of the following types of waves cannot travel through a vacuum?

   • AX-rays
   • BRadio waves
   • CMicrowaves
   • DSound waves
   Show answer & solution

   Correct answer: (D) Sound waves

   Sound is a mechanical wave that requires a material medium to propagate, so it cannot travel through a vacuum; X-rays, radio waves and microwaves are electromagnetic waves that can.

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