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NCERT Solutions for Class 11 Physics Ch-14: Waves
NCERT Solutions for Class 11 Physics Chapter 14 Waves covers the nature and types of mechanical waves, wave speed, the principle of superposition, reflection of waves, and the phenomena of beats and the Doppler effect.
Overview of Topics & Subtopics
Important Questions and Answers
Q1: Differentiate between transverse and longitudinal waves, giving an example of each.
Answer: In a transverse wave, particles of the medium oscillate perpendicular to the direction of wave propagation, as in waves on a stretched string. In a longitudinal wave, particles oscillate parallel to the direction of wave propagation, as in sound waves travelling through air.
Q2: Write the general equation for a progressive (travelling) wave moving in the positive x-direction.
Answer: The general equation for a progressive wave travelling in the positive x-direction is y(x,t) = A sin(kx − ωt + φ), where A is the amplitude, k is the wave number, ω is the angular frequency, and φ is the initial phase constant.
Q3: State the principle of superposition of waves.
Answer: The principle of superposition states that when two or more waves overlap in a medium, the resultant displacement at any point at any instant is equal to the vector (or algebraic) sum of the displacements produced by each individual wave at that point at that instant.
Q4: What are 'beats', and how is the beat frequency calculated?
Answer: Beats are the periodic variation in the intensity of sound heard when two waves of slightly different frequencies superpose. The beat frequency is equal to the absolute difference between the frequencies of the two interfering waves, fbeat = |f1 − f2|.
Q5: What is the Doppler effect?
Answer: The Doppler effect is the apparent change in the frequency (or pitch) of a wave as perceived by an observer due to relative motion between the source of the wave and the observer; the perceived frequency increases when the source and observer approach each other and decreases when they move apart.
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