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New NCERT textbook · Class 9 Science

Exploration, period by period — fitted to your timetable.

Tell Meyy your periods and their length; it plans every chapter of Exploration to fit, and you tick off sections as you teach.

Chapter 10 · Period 1 of 18 · 50 min

Rubber Band and Box: Linking Vibration to Sound Production

10.1 Production of Sound · Hands-on Science

Students may think sound is produced by plucking rather than by the resulting vibration — draw attention to the visible to-and-fro motion of the band during sound and its absence when the sound stops. The comparison between the band on the box and the band alone provides a good opening for discussing how the surrounding medium amplifies vibration into audible sound. Ask students to hold the vibrating band lightly with a fingertip and describe what they feel, connecting touch sensation to the oscillatory motion.

0-8Students stretch a rubber band across an open cardboard box and pluck it, observing and describing what they see and hear while the band vibrates, and noting when sound stops.
8-20Students vary the tension of the rubber band by pressing it at different points and pluck again, recording how the sound changes with tension and whether vibration is still visible each time.
20-35Students remove the rubber band from the box, pluck it in open air, and compare the loudness to the box arrangement, writing a short explanation of why the sounds differ and what role the vibrating object plays.
35-45Class discussion: students share their explanations and together articulate the principle that sound is produced only while an object vibrates, and that the vibrating object is called the source.
45-50Students write a two-sentence summary naming one other vibrating source of sound (vocal cords, string, membrane) and explaining why sound stops when vibration stops.
Assessment

Competency (C-2.7). Describes the origin and properties of sound (wavelength, frequency, amplitude).

Learning outcome. Students can identify the physical condition required for a source to produce sound and explain why sound ceases when that condition is removed.

A student plucks a stretched rubber band and hears a sound. She then presses the rubber band firmly with her finger to stop it moving. What happens to the sound, and why?

  • A The sound continues because the rubber band is still stretched and under tension.
  • B The sound gets softer but does not stop, because the rubber band still holds stored energy.
  • C The sound stops because pressing the band reduces the air pressure around it.
  • D The sound stops because vibration of the rubber band stops.

D. The sound stops because vibration of the rubber band stops.

What each wrong option reveals

  • A Student confuses tension (a static condition) with vibration (a dynamic condition); they think stored mechanical energy in a stretched band is sufficient to produce sound even without motion.
  • B Student holds a partial misconception — that sound decays rather than stops instantly when vibration ceases — possibly from experience of sounds that fade rather than cut off sharply.
  • C Student attributes sound cessation to a pressure mechanism rather than to the vibration of the source; this reveals a gap in understanding what 'source' means in sound production.
Chapter 10 · 18 periods of 50 min

Also saved as 11 periods or 15 periods.

  • 2Tuning Fork Investigation: Confirming Vibration Through Two Observations
    10.1.1 Tuning fork
  • 3Desk Knock and Spoon Tap: Sound Travelling Through Solids and Liquids
    10.2 Propagation of Sound
  • 4Bell Jar Vacuum Experiment: Establishing That Sound Needs a Medium
    10.2.1 Sound needs a medium to propagate
  • 5Slinky Investigation: Modelling Compressions and Rarefactions in Sound
    10.3 Sound Waves
  • 6Grain-Jump Demonstration: Sound Energy Doing Work at a Distance
    10.4 Energy of Sound Waves
  • 7Reading the Density Graph: Crests, Troughs, and Wave Properties
    10.5 Graphical Representation of a Sound Wave
  • 8Wavelength, Frequency, and Time Period: Definitions, Relations, and Calculations
    10.6.1 Wavelength, frequency and time period
  • 9Amplitude, Intensity, and Distance: Analysing How Sound Energy Spreads
    10.6.2 Amplitude and intensity of the sound waves
  • 10Speed of Sound: Deriving v = λν and Applying It Across Contexts
    10.6.3 Speed of Sound
  • 11Pitch, Loudness, and the Human Audible Range: Physical Quantities and Perception
    10.6.4 Human perception of sound
  • 12Laws of Reflection for Sound: Equal Angles and Everyday Acoustic Consequences
    10.7 Reflection of Sound
  • 13Echo Calculation and Minimum Distance: Applying the Reflection Formula
    10.7.1 Echo
  • 14Reverberation and Auditorium Acoustics: Designing for Controlled Sound
    10.7.2 Reverberation
  • 15Infrasonic and Ultrasonic Applications: Range, Use, and Underlying Principle
    10.8 Ultrasonic and Infrasonic Waves, and their Applications
  • 16Echolocation and Sonar: Reflected Ultrasound for Biological and Technological Navigation
    10.8.1 Echolocation
  • 17Sound Energy Conversions and Noise Pollution: Microphones, Speakers, and Hearing Health
    10.6.4 Human perception of sound (Revisit)
  • 18Sound Waves End-to-End: Synthesis Through a Novel Scenario Investigation
    Synthesis
Exploration · Class 9 · 13 chapters

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