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General ScienceMediumAsked in: CDS · CDS-II 2016, GK

Which one of the following statements is not correct?

  1. A.The response of the ear to sound of increasing intensity is approximately logarithmic.
  2. B.The sensitivity of the human ear does not vary with the frequency of the sound.
  3. C.When two or more waves traverse the same medium, the displacement of any element of the medium is the algebraic sum of the displacements due to each wave.
  4. D.Longitudinal waves can travel in all media—solids, liquids and gases.

Correct answer

B. The sensitivity of the human ear does not vary with the frequency of the sound.

Explanation

The correct answer is B. The statement that the sensitivity of the human ear does not vary with frequency is false, because the ear is far more sensitive to some frequencies than to others.

Humans hear roughly from 20 Hz to 20,000 Hz, and the ear is most sensitive between about 2,000 and 5,000 Hz. A very low or very high note must be much more intense to sound as loud as a note in this middle range. That is why equal-loudness curves are not flat and why loudness in phon differs from intensity in decibels.

A is correct because the ear responds roughly to the logarithm of intensity, which is why sound level is measured on the logarithmic decibel scale. C is correct because it is the principle of superposition, the basis of interference and beats. D is correct because longitudinal waves need only a medium that can be compressed, and solids, liquids and gases can all be compressed; transverse waves, by contrast, cannot pass through the bulk of a fluid.

Exam tip: audible range 20 Hz to 20 kHz; the ear is most sensitive near 2 to 5 kHz.

Practice Questions

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Q1.General ScienceAsked in: CDS · CDS-I 2023, GKMedium

Which one of the following is not true for anodizing process?

  1. A.It makes aluminium corrosion resistant.
  2. B.Metals like aluminium, titanium and magnesium can be anodized.
  3. C.Clean aluminium article is the anode and oxygen gas is evolved at the cathode.
  4. D.It is used in aircraft industry.
Show answer
Correct answer: C. Clean aluminium article is the anode and oxygen gas is evolved at the cathode.

In anodizing the clean aluminium article is indeed the anode, but oxygen is released at the anode, not at the cathode; hydrogen is released at the cathode.

Q2.General ScienceAsked in: CDS · CDS-I 2017, GKEasy

Kwashiorkor disease in children is caused by

  1. A.sufficient carbohydrates but less fats in diet
  2. B.sufficient carbohydrates and fats but deficient proteins in diet
  3. C.sufficient vitamins but deficient fats in diet
  4. D.sufficient fats but deficient vitamins in diet
Show answer
Correct answer: B. sufficient carbohydrates and fats but deficient proteins in diet

Kwashiorkor is a disease of protein deficiency in a child who still gets enough calories. It usually appears when a child is weaned from breast milk onto a starchy diet with little protein.

Q3.General ScienceAsked in: CDS · CDS-I 2023, GKMedium

Which one of the following is the correct order of pH for the given substances?

  1. A.Coffee < Lemon juice < Milk of magnesia < Blood
  2. B.Milk of magnesia < Blood < Coffee < Lemon juice
  3. C.Lemon juice < Blood < Coffee < Milk of magnesia
  4. D.Lemon juice < Coffee < Blood < Milk of magnesia
Show answer
Correct answer: D. Lemon juice < Coffee < Blood < Milk of magnesia

Arranged from most acidic to most basic, the four substances fall in exactly this order. Lemon juice, rich in citric acid, has a pH of about 2 to 2.5.