You are here
💡 Seeing with sound
A bat flies in pitch dark and never crashes — it ‘sees’ the world with echoes.
What is echolocation?
Echolocation
Locating objects by sending ultrasonic waves and sensing the reflected echoes; used by bats, dolphins and in SONAR.
- 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 would sense sounds that are hidden from us today.
- That could be useful for warnings and for diagnostics.
- But machines and electronics would also become audible.
- Everyday life would be far noisier — 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.
View Answer →
⏸▶ Pause and Ponder
- 12. For an echo at least 0.2 s later at 343 m/s: total path =343× 0.2=68.6 m , so minimum distance = 68.6 2 = 34.3 m .
⏸▶ Pause and Ponder
- 13. A sonar signal sent to find the depth of the ocean takes 4 s to return. What is the depth if the speed of sound in seawater is 1500 m s⁻¹?
- 4 s is the time for the down and back journey.
- Time for one way = 4 2 =2 s .
- Depth = speed × time =1500× 2 .
- Depth = 3000 m .
✅ Test Yourself
-
What are infrasonic waves?
Show Answer
Sound waves with frequency below 20 Hz . -
What are ultrasonic waves?
Show Answer
Sound waves with frequency above 20 kHz . -
What is echolocation?
Show Answer
Locating objects using reflected sound waves — as bats and dolphins do. -
What does SONAR stand for?
Show Answer
Sound Navigation and Ranging. -
Name two medical uses of ultrasound.
Show Answer
Ultrasonography (imaging organs) and breaking kidney stones.
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.
