Question

Bats detect the obstacle in their path by receiving the detected:
A. infrasonic waves
B. ultrasonic waves
C. both
D. none

Answer 1

Hint: Firstly, we need to know the difference between ultrasonic and infrasonic waves to answer this question as both may be confused. Sound waves that are divided according to their respective frequencies must be known to answer this question. Once we know the purpose of each wave and its source, we can know what waves the bats use to detect the obstacles.

Complete answer:
Sound is a disturbance or wave which transmits through a medium. Based on the frequency of the sound, it is divided into three kinds. They are:
1. Infrasonic waves
2. Acoustic waves
3. Ultrasonic waves
Let us start with acoustic waves, to understand the other kinds better.
Acoustics or audible sound is the sound we hear on a daily basis. It is in the frequency range of 20 Hz to 20 kHz. Humans can hear the sounds which are only under this frequency range.
Now, the infrasonic waves are those which have frequency lesser than that of 20Hz. These are not audible. These waves are produced by earthquakes, volcanoes, meteors, etc. Animals can also generate infrasonic waves. Some of the animals that communicate through infrasonic waves are whales, giraffes, rhinoceros, elephants, etc. Infrasonic waves are said to have a bad effect on humans, at high decibels.
The ultrasonic waves are sound waves that have a frequency higher than 20kHz. Even these waves are inaudible. Ultrasonic waves are also produced by animals in detecting their prey. These animals include bats, dolphins, moths, etc.

So, the correct answer is “Option B”.

Note:
Infrasonic is below audible range and Ultrasonic is above the audible range. The dogs and cats can also detect ultrasonic waves. The technique used by the bats is known as echolocation. The bats initially generate ultrasonic waves. The waves which return back give the bat an image of the surrounding or prey as a disturbance in the wave. The same technique is used in SONAR and ultrasound imaging.