We hear an echo due to

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NDA-I (GAT) Official Paper (Held On: 13 Apr, 2025)
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  1. Refraction of sound waves
  2. Reflection of sound waves
  3. Diffraction of sound waves
  4. Resonance due to sound waves

Answer (Detailed Solution Below)

Option 2 : Reflection of sound waves
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Detailed Solution

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Concept:

Echo: An echo is the reflection of sound that arrives at the listener after a delay, caused by the sound wave bouncing off a surface.

Reflection of sound: When sound waves hit a hard surface, they bounce back, creating a reflected sound wave.

Conditions for echo formation:

The distance between the source and reflecting surface should be at least 17.2 meters (for sound velocity ~344 m/s).

The surface should be large and hard.

∴ he correct answer is Option 2: Reflection of sound waves.

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