Reflection Of Sound

Key Notes:

1️⃣ What is Reflection of Sound?

• Reflection of sound is the bouncing back of sound waves when they strike a hard surface like a wall, cliff, or building.
• It is similar to the reflection of light but involves sound waves.

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2️⃣ Laws of Reflection of Sound

The reflection of sound follows the same laws as light:

• Angle of incidence = Angle of reflection
• The incident sound wave, reflected sound wave, and the normal all lie in the same plane.

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3️⃣ Echo 🎤

• An echo is the repetition of sound heard after it reflects from a distant surface.
• For an echo to be heard clearly:
  • Time gap ≥ 0.1 seconds
  • Distance of reflecting surface ≥ 17 meters (in air)
• Example: Shouting near a hill or inside a large empty hall.

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4️⃣ Multiple Reflection of Sound

• When sound reflects more than once, it is called multiple reflection.
• Examples:
  • Sound in concert halls
  • Megaphones, loudhailers
  • Stethoscope

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5️⃣ Uses of Reflection of Sound

• SONAR: Used to measure depth of the sea and locate underwater objects.
• Stethoscope: Helps doctors hear heartbeats.
• Soundboards in auditoriums help distribute sound evenly.

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6️⃣ Reverberation 🔁

• Reverberation is the persistence of sound caused by repeated reflections in an enclosed space.
• Too much reverberation makes sound unclear.
• Reduced by using:
  • Curtains
  • Carpets
  • Acoustic panels

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7️⃣ Difference Between Echo and Reverberation

Echo	Reverberation
Heard as a distinct sound	Sound overlaps and continues
Requires large distance	Occurs in enclosed spaces
Time gap ≥ 0.1 s	Time gap < 0.1 s

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8️⃣ Important Exam Points ⭐

• Reflection of sound helps us hear sounds clearly in halls.
• Hard surfaces reflect sound better than soft surfaces.
• Used in medical, marine, and communication fields.