Factors Affecting the Speed of Sound in a Gas | Class 9 Physics | Propagation of Sound Waves

💨 Why does sound travel faster on a hot summer day than on a cold winter morning? In this Class 9 ICSE Physics video, we explore the Factors Affecting the Speed of Sound in a Gas.
You’ll learn how elasticity and density influence sound speed and how temperature, molecular weight, and humidity further modify the value.
We’ll explain why lighter gases like helium transmit sound faster, why humid air carries sound better than dry air, and how temperature directly increases velocity using the gas law relation:
A solved numerical example shows speed calculation in air at 27°C, and we finish with a crisp summary for exam-ready learning.

📚 What You’ll Learn in This Video
1️⃣ Role of elasticity and density in sound speed.
2️⃣ Effect of temperature on speed in gases: v∝Tv \propto \sqrt{T}v∝T​.
3️⃣ Effect of molecular weight – lighter gases transmit faster.
4️⃣ Role of humidity in increasing sound speed.
5️⃣ Solved Example – Speed of sound in air at 27°C.
6️⃣ Summary – Key equations and factors explained.

🎯 Why Watch This Video?
✔ Exam-Oriented – Focus on ICSE Class 9 Concept 7.
✔ Concept Clarity – Explains how each factor modifies speed.
✔ Solved Example – Step-by-step numerical with formula.
✔ Real-Life Relevance – Understand thunder delay, summer vs winter sound travel.
✔ Board-Focused – Useful for ICSE, CBSE, and State Boards.

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