CBSE Class 8 Civics - Indian Constitution important notes. Learning the important concepts is very important for every student to get better marks in examinations. The concepts should be clear which will help in faster learning. The attached concepts made as per NCERT and CBSE pattern will help the student to understand the chapter and score better marks in the examinations.
NOTES TERM –I
Q1. Define the term Vibration?
Ans. To & fro or back & forth motion of an object is called vibration.
Q2. How is sound produced?
Ans. Sound is produced when an object vibrates.
Q3. Name the part which vibrates to produce sound in the following:
(a) Drums (b) Veena (c) Flute (d) Tabla
Ans. (a) Stretched membrane (b) Stretched string © Air column (d) Stretched membrane
Q4. Name the sound producing organ in humans.
Ans. Voice box or Larynx.
Q5. Describe how sound is produced by the human voice box (or larynx)?
Ans. Two vocal cords are stretched across the voice box or larynx in such away that it leaves a narrow slit between themfor the passage of air. When the lung force air through the slit, the vocal cords vibrate to produce sound,
Q6. What is the frequency of the sound produced when the vocal cords are:
(a) Tight & thin? (b) Loose & thick?
Ans. (a) High frequency (high pitch sound). (b) Low frequency (low pitch sound).
Q7. Why are voices of men, women & children different?
Ans. The lengths of the vocal cords are different in men, women & children; as a result sounds of different frequencies (or different pitch) are produced.
Q8. Why a sound cannot be heard on the moon?
Ans. Sound needs amedium ( ie. Solid, liquids or gas) for its propagation. Since there is no atmosphere on the moon to carry the sound waves, therefore sound cannot be heard on moon.
Q9. Out of solids, liquids & gases:
(a) In which medium sound travels slowest?
(b) In which medium sound travels the fastest?
Ans. (a Gases. (b Solids.
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