Sound · ध्वनि

Why can't sound travel in space? What makes a sound high or loud?

Sound games

Sound is made by vibrations and travels as a longitudinal wave (compressions and rarefactions).
It needs a medium — solids > liquids > gases; not through vacuum.
Frequency (Hz) decides pitch; amplitude decides loudness (dB).
Audible range 20 Hz – 20 kHz; below = infrasound (elephants), above = ultrasound (bats, dolphins, scans).
Echo: reflected sound; SONAR uses it to measure sea depth.

For Class 8 and 9 (NCERT Exploration 9, “Sound Waves”).

A one-page chart to stick on the wall, and a worksheet to practise.

Vibration → sound. Needs a medium. Pitch ↔ frequency, loudness ↔ amplitude. 20 Hz – 20 kHz.

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Name: ____________________ Class: ______ Date: __________

1. Why can't astronauts talk directly on the Moon?

2. Difference between pitch and loudness?

3. What is an echo? Give one use of ultrasound.

kheloaurseekho.in — free charts, games and worksheets