17
Question Question 17
Explain how defects in a metal block can be detected using ultrasound.
Ultrasonic waves are allowed to pass through the metal block and detectors are used to detect the transmitted waves. If there is even a small defect, the ultrasound gets reflected back indicating the presence of the flaw or defect, as shown below:
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