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💡 Seeing with sound
A bat flies in pitch dark and never crashes — it ‘sees’ the world with echoes.
What is echolocation?
- Bats emit short bursts of ultrasonic waves that reflect off nearby objects.
- By sensing the returning echoes , a bat finds the position of obstacles and prey.
- Locating objects using reflected sound is called echolocation — also used by dolphins, whales and in SONAR.
❓ What if…
What if humans could detect ultrasonic waves like dogs? We could sense sounds hidden from us today (useful for warnings and diagnostics), but everyday noise from machines and electronics would also become audible — a real trade-off.
NCERT Question 11 — A vehicle is fitted with
A vehicle is fitted with an ultrasonic distance sensor as part of parking assistance system which provides echolocation, while the driver is reversing the vehicle. It emits ultrasonic wave (about 40 kHz) which is reflected by the obstacle. When the warning beep starts sounding at a distance of 1.2 m from the obstacle, how much time is taken by ultrasonic wave to travel to the obstacle and come back? Assume the speed of ultrasonic wave in air to be 345 m s⁻¹.
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⏸▶ Pause and Ponder
- 12. For an echo at least 0.2 s later at 343 m/s: total path \(=343\times 0.2=68.6\ \text{m}\), so minimum distance \(=\dfrac{68.6}{2}=\mathbf{34.3}\ \text{m}\).
- 13. Sonar depth: time one way \(=\dfrac{4}{2}=2\ \text{s}\); depth \(=1500\times 2=\mathbf{3000}\ \text{m}\).
Important Definitions
- Echolocation — locating objects using reflected ultrasonic waves, as bats and dolphins do.
- SONAR — Sound Navigation and Ranging - using ultrasound to find the distance and direction of underwater objects.
