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Chapter Analysis
Intermediate22 pages • EnglishQuick Summary
The chapter 'Waves' in Class 11 Physics explores the nature and properties of waves, detailing how mechanical waves transfer energy through a medium without actually transporting matter. It distinguishes between transverse and longitudinal waves, explaining their characteristics and mechanisms. The chapter covers wave properties such as wavelength, frequency, and speed and delves into the principles of superposition, reflection, and standing waves. Through these discussions, students learn about the underlying principles governing wave motion and their relevance in real-world applications, such as sound and light propagation.
Key Topics
- •Transverse and Longitudinal Waves
- •Wave Properties: Wavelength, Frequency, Speed
- •Principle of Superposition
- •Reflection and Standing Waves
- •Interference of Waves
- •Beats and Harmonic Oscillations
- •Mechanical vs Electromagnetic Waves
Learning Objectives
- ✓Understand the distinction between transverse and longitudinal waves.
- ✓Explain the propagation of mechanical waves through different media.
- ✓Apply the principle of superposition to wave interactions.
- ✓Analyze the behavior of waves at boundaries and the formation of standing waves.
- ✓Identify and calculate the parameters affecting wave speed.
- ✓Interpret the physical implications of wave interference phenomena.
Questions in Chapter
A string of mass 2.50 kg is under a tension of 200 N. The length of the stretched string is 20.0 m. If the transverse jerk is struck at one end of the string, how long does the disturbance take to reach the other end?
Page 297
Use the formula v = √(γP/ρ) to explain why the speed of sound in air (a) is independent of pressure, (b) increases with temperature, (c) increases with humidity.
Page 298
A bat emits ultrasonic sound of frequency 1000 kHz in air. If the sound meets a water surface, what is the wavelength of (a) the reflected sound, (b) the transmitted sound? Speed of sound in air is 340 m s–1 and in water 1486 m s–1.
Page 298
A transverse harmonic wave on a string is described by y(x, t) = 3.0 sin (36 t + 0.018 x + π/4). What are the speed and direction of its propagation?
Page 299
A pipe 20 cm long is closed at one end. Which harmonic mode of the pipe is resonantly excited by a 430 Hz source? Will the same source be in resonance with the pipe if both ends are open?
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Additional Practice Questions
Explain the difference between transverse and longitudinal waves with examples.
easyAnswer: Transverse waves are characterized by particle motion perpendicular to the direction of wave propagation, like ripples on a pond. Longitudinal waves feature particle displacement parallel to the wave direction, such as sound waves in air.
Describe the phenomenon of constructive and destructive interference.
mediumAnswer: Constructive interference occurs when waves combine to produce a wave with a larger amplitude, while destructive interference results in cancellation or reduced amplitude when waves are out of phase.
What is the principle of superposition and how does it apply to wave interactions?
mediumAnswer: The principle states that when two or more waves overlap, the resultant displacement is the sum of the individual displacements. This principle explains phenomena like interference patterns and beats.
How does wave speed in a medium depend on its properties?
hardAnswer: Wave speed is typically dependent on medium properties such as tension and mass density in the case of mechanical waves, with the speed formula being v = √(tension/mass density).
Calculate the frequency of a standing wave on a string with a length of 1m fixed at both ends given a wave speed of 100 m/s.
hardAnswer: The frequency is calculated using the formula v = n(v/2L) where L is the string length. For the fundamental mode (n=1), the frequency is 50 Hz.