UPSC CDS-1

41. Which one of the following is not a property of the X-rays?

Which one of the following is not a property of the X-rays?

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They are deflected by electric fields.
They are not deflected by magnetic fields.
They have high penetration length in matter.
Their wavelength is much smaller than that of visible light.
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UPSC CDS-1 – 2020
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X-rays are a form of electromagnetic radiation, consisting of photons. Unlike charged particles (like electrons or protons), uncharged particles like photons are generally not deflected by static electric or magnetic fields when traveling through a vacuum or air. Statement A claims they are deflected by electric fields, which is not a general property of X-rays as electromagnetic waves.
– X-rays are electromagnetic waves.
– Electromagnetic waves are not deflected by static electric or magnetic fields.
– X-rays have high penetration power and short wavelengths compared to visible light.
X-rays can be scattered by matter, and this scattering can be influenced by electromagnetic fields within the material, but the direct path of an X-ray beam is not bent by external static electric or magnetic fields in the way charged particles are.

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42. The property of the sound waves that determines the pitch of the sound

The property of the sound waves that determines the pitch of the sound is its

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frequency
amplitude
wavelength
intensity
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The pitch of a sound is the quality that allows us to judge whether a sound is high (like a whistle) or low (like a drum). This quality is directly determined by the frequency of the sound wave. A higher frequency corresponds to a higher pitch, and a lower frequency corresponds to a lower pitch.
– Pitch is the subjective perception of the frequency of sound.
– Higher frequency means higher pitch.
– Amplitude relates to loudness or intensity.
While frequency is the primary determinant of pitch, other factors like the intensity of the sound can also slightly influence the perceived pitch, especially at very high or very low frequencies. However, for practical purposes, frequency is considered the defining characteristic for pitch.

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43. Match List-I with List-II and select the correct answer using the code

Match List-I with List-II and select the correct answer using the code given below the Lists :

List-I
(Compound)		 List-II
(Use)
A. Boric acid 1. Antiseptic
B. Citric acid 2. Food preservative
C. Magnesium hydroxide 3. Antacid
D. Acetic acid 4. Pickle

Code :

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A-1, B-2, C-3, D-4
A-1, B-3, C-2, D-4
A-4, B-3, C-2, D-1
A-4, B-2, C-3, D-1
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The matching is as follows:
– A. Boric acid: Known for its mild antiseptic properties, often used in eyewashes and topical applications.
– B. Citric acid: A common food additive used as a preservative due to its acidic nature and antioxidant properties.
– C. Magnesium hydroxide: A component of antacids (like Milk of Magnesia) used to neutralize excess stomach acid.
– D. Acetic acid: The main component of vinegar, commonly used in pickling as both a flavouring agent and preservative.
Thus, the correct mapping is A-1, B-2, C-3, D-4.
– Boric acid acts as an antiseptic.
– Citric acid functions as a food preservative.
– Magnesium hydroxide is used as an antacid.
– Acetic acid is used in pickles.
Many substances have multiple uses. For instance, citric acid is also used in cleaning products and cosmetics. Magnesium hydroxide is also used as a laxative at higher doses.

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44. Which one of the following acids is produced in human stomach?

Which one of the following acids is produced in human stomach?

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Formic acid
Sulphuric acid
Nitric acid
Hydrochloric acid
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UPSC CDS-1 – 2020
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The human stomach produces gastric acid, which is primarily composed of hydrochloric acid (HCl). This acid creates a highly acidic environment in the stomach (pH typically between 1.5 and 3.5), which is essential for activating the enzyme pepsin for protein digestion and killing ingested pathogens.
– Hydrochloric acid (HCl) is the main acid present in gastric juice.
– Gastric acid helps in digestion and provides protection against microorganisms.
Other components of gastric juice include pepsinogen, mucus, and intrinsic factor. Formic acid, Sulphuric acid, and Nitric acid are not naturally produced in the human stomach.

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45. A solution having pH equal to zero is known as

A solution having pH equal to zero is known as

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highly alkaline solution
highly acidic solution
weakly acidic solution
neutral solution
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The pH scale measures the acidity or alkalinity of a solution. A pH value of 7 indicates a neutral solution. Values less than 7 indicate acidic solutions, with decreasing pH corresponding to increasing acidity. Values greater than 7 indicate alkaline (basic) solutions, with increasing pH corresponding to increasing alkalinity. A pH of zero represents a high concentration of hydrogen ions, characteristic of a very strong acidic solution.
– pH is defined as the negative logarithm of the hydrogen ion concentration ([H+]).
– pH < 7 is acidic, pH > 7 is alkaline, pH = 7 is neutral.
– A lower pH indicates higher acidity.
While the standard pH scale usually ranges from 0 to 14, highly concentrated strong acids can have negative pH values, and highly concentrated strong bases can have pH values greater than 14. A pH of 0 is within the range of very acidic solutions.

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46. Which one of the following chemical reactions is not feasible?

Which one of the following chemical reactions is not feasible?

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Fe + CuSO₄ → FeSO₄ + Cu
Zn + CuSO₄ → ZnSO₄ + Cu
Cu + PbCl₂ → CuCl₂ + Pb
Mg + CuSO₄ → MgSO₄ + Cu
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UPSC CDS-1 – 2020
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A chemical reaction where a metal displaces another metal from its salt solution is feasible only if the displacing metal is more reactive than the metal being displaced. The reactivity series of metals dictates this.
Comparing the reactivity of the metals involved: Magnesium (Mg) > Zinc (Zn) > Iron (Fe) > Lead (Pb) > Copper (Cu).
– A) Fe + CuSO₄: Fe is more reactive than Cu. Fe displaces Cu. Feasible.
– B) Zn + CuSO₄: Zn is more reactive than Cu. Zn displaces Cu. Feasible.
– C) Cu + PbCl₂: Cu is less reactive than Pb. Cu cannot displace Pb. Not feasible.
– D) Mg + CuSO₄: Mg is more reactive than Cu. Mg displaces Cu. Feasible.
The reactivity series is determined experimentally and shows the relative tendency of metals to lose electrons and form positive ions. More reactive metals are higher in the series.

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47. The elements of which of the following pairs are isobars?

The elements of which of the following pairs are isobars?

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¹₁H and ³₁H
¹₁H and ²₁H
¹²₆C and ¹⁴₆C
⁴⁰₁₈Ar and ⁴⁰₂₀Ca
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Isobars are atoms of different chemical elements that have the same mass number (number of protons + neutrons) but different atomic numbers (number of protons).
In option D, ⁴⁰₁₈Ar (Argon) has an atomic number (Z) of 18 and a mass number (A) of 40. ⁴⁰₂₀Ca (Calcium) has an atomic number (Z) of 20 and a mass number (A) of 40. Since they have different atomic numbers but the same mass number, they are isobars.
Options A, B, and C show pairs of isotopes, which are atoms of the same element (same atomic number) but different mass numbers.

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48. Scattering of α-particles by a thin gold foil suggests the presence o

Scattering of α-particles by a thin gold foil suggests the presence of

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electron in an atom
proton in an atom
positively charged nucleus at the centre of an atom
isotopes of gold
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UPSC CDS-1 – 2020
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Rutherford’s alpha-particle scattering experiment demonstrated that a small, dense, positively charged nucleus exists at the center of an atom.
The deflection of positively charged alpha particles at large angles, and the reflection of a few back towards the source, indicated that they were encountering a strong positive charge concentrated in a very small volume within the atom, which was termed the nucleus.
The vast majority of alpha particles passed straight through the gold foil, leading to the conclusion that most of the atom’s volume is empty space. This experiment disproved the plum pudding model of the atom.

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49. The 11th BRICS Summit in 2019 will be hosted by

The 11th BRICS Summit in 2019 will be hosted by

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China
Russia
Brazil
India
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The BRICS summit host country rotates annually among the member states in the order of the acronym BRICS.
The 10th BRICS summit was held in South Africa in 2018. Following the rotation (Brazil, Russia, India, China, South Africa), the 11th summit in 2019 was hosted by Brazil.
The BRICS summit in 2019 was held in Brasilia, Brazil. Subsequent summits followed the rotation: Russia (2020), India (2021), China (2022), South Africa (2023).

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50. Which of the following are the benefits of the Pradhan Mantri Jan Arog

Which of the following are the benefits of the Pradhan Mantri Jan Arogya Yojana (PMJAY)?

  • 1. Free treatment available at all public and empanelled private hospitals in times of need
  • 2. Cashless and paperless access to quality health-care services
  • 3. Government provides health insurance cover of up to ₹ 5,00,000 per family per year
  • 4. Pre-existing diseases are not covered

Select the correct answer using the code given below.

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1 and 3 only
1, 2 and 3
2 and 4 only
2, 3 and 4
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UPSC CDS-1 – 2019
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Statements 1, 2, and 3 correctly describe the benefits of the Pradhan Mantri Jan Arogya Yojana (PMJAY). Statement 4 is incorrect.
PMJAY provides a health cover of up to ₹ 5 lakh per family per year for secondary and tertiary hospitalization. It aims to provide cashless and paperless access to healthcare at public and empaneled private hospitals. Importantly, it covers pre-existing diseases from day one, unlike many conventional insurance schemes.
PMJAY is the world’s largest health insurance scheme sponsored by the government. It is a component of the Ayushman Bharat programme and covers over 10.74 crore poor and vulnerable families (approximately 50 crore beneficiaries).

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