Physics
For an echo, the reflected sound must reach the person at least …………… after the original sound is heard.
- 1 s
- 10 s
- 0.1 s
- 0.01 s
Answer
0.1 s
Reason — For an echo to be heard, the reflected sound must reach the listener's ears at least 0.1 seconds (or 100 milliseconds) after the original sound is produced. If the reflected sound arrives sooner than this, it is perceived as part of the original sound rather than as a distinct echo.
Related Questions
With the increase in temperature of a gas, the speed of sound:
- decreases
- increases
- remains the same
- cannot say
The condition for reflection of sound wave is :
- surface must be smooth
- surface must be polished
- reflecting surface must be bigger than the wavelength of the sound wave
- reflecting surface must be smaller than the wavelength of the sound wave
The minimum distance between the source and the reflector in air, to hear an echo, is approximately:
- 10 m
- 17 m
- 34 m
- 50 m.