11
Question Question 11
Give two practical applications of the reflection of sound waves.
Two practical applications of the reflection of sound waves are:
- Stethoscope — It is a medical device used to hear sounds within the body mainly heartbeat. In stethoscopes the sound of the patient's heartbeat reaches the doctor's ears by multiple reflection of sound.
- Curved ceilings of concert halls — Generally the ceilings of concert halls, conference halls and cinema halls are curved so that sound after reflection reaches all corners of the hall.
BRIGHT TUTORIALS
BRIGHT TUTORIALS
CBSE Class IX | Academic Year 2026-2027
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Science | Chapter 11: SoundWeb Content — Quick Reference
Chapter 11: Sound — Quick Reference
Quick Revision Points
- Sound: produced by vibration, needs medium, longitudinal wave (compressions + rarefactions)
- v = fλ; Speed in air ≈ 344 m/s; Solids > Liquids > Gases
- Loudness → amplitude; Pitch → frequency; Quality → waveform
- Echo: reflected sound; min distance = 17.2 m (at v = 344 m/s, t ≥ 0.1 s)
- Audible range: 20 Hz – 20 kHz; Infrasound < 20 Hz; Ultrasound > 20 kHz
- SONAR: d = vt/2; Human ear: pinna → canal → eardrum → hammer/anvil/stirrup → cochlea → auditory nerve
Exam Tips for Chapter 11
- Read the detailed chapter notes for complete coverage of all NCERT topics.
- Practice all NCERT in-text and back exercise questions — they are frequently asked in exams.
- Focus on comparison tables, diagrams, and definitions — these are high-scoring areas.
- For numericals (if applicable), practice at least 20 problems of varying difficulty.
- Refer to the practice question bank (200+ questions) for thorough preparation.
Related Resources
- Detailed Notes: ch11-sound.html
- Practice Questions: 100+ questions with answers in 05-practice-questions/
- Chapter Test: 30-mark test paper in 06-tests/chapter-tests-30marks/
- Formula Sheet: Complete formula reference in 03-teacher-aid/formula-sheet.html