Test: Ultrasound And Human Ear

10 Questions MCQ Test Science Class 9 | Test: Ultrasound And Human Ear

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Which waves are employed in SONAR?


Another popular use for ultrasonics is in ships, both for navigation and for locating objects underwater. Sound travels faster through water than through air, which is very helpful because light hardly travels through water at all. Most people know that whales can use low-frequency sound to communicate across entire oceans. Submarinesuse a similar trick with a type of navigation called sonar (sound navigation and ranging), which is a bit like an underwater equivalent of radar.


A person clapped his hands near a cliff and heard the echo after 5 sec. What is the distance of the cliff from the person, if the speed of the sound V is taken as 346 ms-1 ?


Speed of sound in air, v = 342 ms^-1

Time taken for hearing the echo, t = 3 s 

Distance  travelled by the sound = vt 

= 342 * 3 

= 1026 m

In 3 s, sound has to travel twice the distance between the the cliff and the person. 

Hence the distance between the cliff and the person is given by, d=  1730 m/2 = 865 m


The vibrations or the pressure variations inside the inner ear are converted into electrical signals by the:


The middle ear transmits the amplified pressure variations received from the sound wave to the inner ear. In the inner ear, the pressure variations are turnedinto electrical signals by the cochlea. These electrical signals are sent to the brain via the auditory nerve, and the brain interprets them as sound.


Which part of the ear amplifies the vibrations of eardrum?


The pressure from sound waves makes the eardrum vibrate. The vibrations are transmitted further into the ear via three bones in the middle ear: the hammer(malleus), the anvil (incus) and the stirrup (stapes).


Sound of the frequency below 20 Hz is known as


Human beings can normally hear sounds with a frequency between about 20 Hzand 20,000 Hz. Sounds with frequencies below 20 hertz are called infrasound.Infrasound is too low-pitched for humans to hear. Sounds with frequencies above 20,000 hertz are called ultrasound.


The technique used by bats to find their way or to locate food is


 The technique used by bats to find their way or to locate food is echo-location


Ultrasound is not used to:


When bats detect ultrasonic waves which after touching the prey comes back to bats ear which tell them how far their prey is and how it looks like. Similarly people detect ultrasonic waves to know the distance. the waves touch the building and comes back which tells us how far it is.


Young children below 5 year can hear up to a frequency of


Its all because Children below 5-6 years and some small animals like cat, dog, rat etc.. have innovation Sound hearing that's why they can hear sound upto 25Khz.


The velocity of ultrasonic sound in water is 1400 m. The depth of the ocean as detected by SONAR, if the time taken to receive the reflected wave is 15s, is



A ship on the surface of water sends a signal and receives it back after 4 seconds from a submarine inside the water. Calculate the distance of the submarine from the ship (The speed of sound in water is 1450 m/s).


2 D = velocity X time
D = (velocity X time) / 2 = 1450 X 4 / 2 = 2900 m = 2.9 km

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