Advertisements
Advertisements
Question
Explain how is the principle of echo used by
(a) The bat during its flight at night,
(b) The dolphin to locate small fish as its prey.
Advertisements
Solution
(a) Bats can produce and detect the sound of very high frequency. The bats fly with speed much lower than the speed of sound. The sounds produced by flying bats get reflected from any obstacle in front of it. By hearing the echoes, bats come to know where the obstacles are, even in the dark. So, they can fly safely without colliding with the obstacles. This process of detecting obstacles is called sound ranging.
(b) Dolphins detect their enemies and small fishes by emitting ultrasonic waves in all directions and then hearing their reflected sound i.e. echo. Dolphins can judge the nature of obstacles or of small fish by hearing the echo and catch their prey.
APPEARS IN
RELATED QUESTIONS
The human ear can detect continuous sounds in the frequency range from 20 Hz to 20,000 Hz. Assuming that the speed of sound in air is 330 m s−1 for all frequencies, calculate the wavelengths corresponding to the given extreme frequencies of the audible range.
How is the frequency of a stretched string related it’s tension?
Define wave velocity term in relation to a wave.
A wave passes from one medium to another medium. Mention one property of the wave out of speed, frequency or wavelength which changes.
State two differences between the light and sound waves.
What do you mean by reflection of sound? State one condition for the reflection of a sound wave. Name a device in which reflection of sound wave is used.
Mention two properties of a wave, one property which varies and the other which remains constant when the wave passes from one medium to another.
What are fishing boats?
Waves produced on the surface of the water are formed to move with a velocity of 24 ms−1. If the wavelength of these waves equals 20 cm. find the
(i) frequency (no. of waves produced per second)
(ii) the time period (i.e. the time required to produce one wave) for these waves.
