Echoes | Year 7 Physics (Cambridge) - Class 7 PDF Download

Reflection of Sound

• Definition: Reflection of sound waves is known as an echo.
• Example: When sound waves hit a wall, some are absorbed and some reflect back, creating an echo.
• Impact of Environment: Empty rooms amplify echoes; soft furnishings like carpets reduce echo effects.

Using Echoes to Measure Speed of Sound

• Equation: Speed of sound (v) = Distance (d) / Time (t)
• Example Calculation:
  • If echo heard in 2 seconds, and distance to wall is 340 meters, total distance traveled = 680 meters.
  • Calculation: 
• Calculating Distance Using Echoes: Distance (d) = Speed (v) × Time (t)

Ultrasound

• Definition: Sound waves above 20,000 Hz, beyond human hearing range.
• Animal Use: Bats use echolocation (emitting and detecting ultrasound echoes) for navigation and hunting.
• Medical Use: Ultrasound imaging in medicine uses echoes to visualize internal organs, such as imaging a baby in the womb.
• Marine Use: Ships use sonar (ultrasound echoes) for underwater navigation, calculating distances to objects like the seabed.

Conclusion

Understanding echoes and ultrasound is crucial in various fields, from animal navigation to medical diagnostics and maritime navigation.