Class IX :: Chapter 12 - SOUND
Chapter-wise Multiple Choice Questions with Instant Feedback
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- Sound Production: Sound is produced by vibrating objects and requires a medium to travel.
- Longitudinal Waves: Sound waves are longitudinal—particles vibrate parallel to wave direction.
- Compression & Rarefaction: Compression is high-pressure region; rarefaction is low-pressure region.
- Wave Characteristics: Frequency (Hz), Wavelength (m), Amplitude, Time Period (s), Speed (m/s).
- Wave Formula: Speed = Frequency × Wavelength (v = fλ).
- Sound Properties: Loudness depends on amplitude; Pitch depends on frequency; Quality distinguishes sounds.
- Audible Range: 20 Hz – 20,000 Hz for humans.
- Infrasonic: Below 20 Hz; Ultrasonic: Above 20,000 Hz.
- Reflection of Sound: Echo is reflected sound; minimum 17 m needed for distinct echo (at 340 m/s).
- Reverberation: Persistence of sound due to repeated reflections in enclosed spaces.
- SONAR: Sound Navigation And Ranging—uses ultrasound to detect underwater objects.
- Human Ear: Pinna → Ear canal → Eardrum → Ossicles → Cochlea → Auditory nerve.
- Speed of Sound: Solids > Liquids > Gases; increases with temperature and humidity.
- Applications of Ultrasound: Cleaning, medical imaging (sonography), detecting flaws, echolocation.
Basic Level Questions
Chapter Summary
Sound introduces you to the fascinating world of acoustic physics—exploring how sound is produced, how it travels through different media, and how we perceive it. You'll move beyond simply hearing sounds to understanding the science behind vibrations, wave propagation, and the characteristics that make each sound unique. This chapter connects everyday experiences like echoes, music, and medical ultrasounds to fundamental physics principles.
"Sound" is a high-scoring chapter for Class 9 board exams (CBSE, ICSE, State Boards) and competitive tests like NTSE and Science Olympiads. Exam questions typically include defining key terms, distinguishing between wave types, numerical problems on speed-frequency-wavelength relationships, echo calculations, SONAR applications, and diagram-based questions on the human ear. Mastering this chapter ensures you can confidently solve both conceptual and numerical problems.
Our platform transforms your theoretical knowledge into exam-ready expertise. With a comprehensive collection of graded MCQs—from basic definitions to challenging numerical problems on echo timing, wave speed, and ultrasound applications—you can systematically test every concept. Regular practice helps you quickly recall formulas, avoid common mistakes in calculations, and understand the practical applications of sound technology. This targeted preparation builds speed, accuracy, and confidence, ensuring you can tackle any sound-related question in your exams.