Answer:
The sound waves produced bounce back or gets reflected from the mountain or buildings and come to our ears, this reflected sound is known as Echo. To hear echo, the barrier reflecting the sound should be least at a distance of 17 meters.
Sound
Q 1.
Fill in the blanks :
If a body repeats its back and forth, to and fro or up and down motion along a certain path, about a fixed point, in a certain time interval then the motion of such objects is said to be _____________.
Q 2.
What is speed of sound in air?
Q 3.
Fill in the blanks :
The principle on which stethoscope works is _____ (reflection/ multiple reflection)
Q 4.
What type of wave is represented by density- distance graph?
Q 5.
Distinguish between loudness and intensity of sound.
Q 6.
What is Sound? Why it is important for us?
Q 7.
Fill in the blanks :
In the case of ____________ wave, distance between two consecutive crests or troughs is known as wavelength.
Q 9.
What are ultrasonics?
Q 10.
What are wavelength, frequency, time period and amplitude of a sound wave?
Q 11.
How is ultrasound used for cleaning ?
Q 12.
Fill in the blanks :
RADAR (Radio Detection And Ranging) works on _____________ principle which is used to determine the velocities and movement of aircrafts.
Q 13.
What is reverberation?
Q 14.
Draw a curve showing density or pressure variations with respect to distance for a disturbance produced by sound.Mark the position of compression and rarefaction on this curve.Also define wavelengths and time period using this curve.
Q 15.
What is audible range ?
Q 16.
How can you make a building sound proof ?
Q 17.
Why are the ceilings of concert halls curved ?
Q 18.
What is sound barrier ?
Q 20.
A wave of wavelength 0-60 cm is produced in air and it travels at a speed of 300 m/s.Will it be audible ?
Q 21.
Radio Ceylon broadcasts at 25 m.What is the frequency of the station ?
Q 22.
Distinguish between loudness and intensity of sound.
Q 23.
Cite an experiment to show that sound needs a material medium for its propagation.
Q 24.
What is loudness of sound ? What factors does it depend on ?
Q 25.
What are transverse waves ?
Q 26.
What is SONAR ? How is it used to detect an underwater object and measure its distance
Q 27.
Fill in the blanks :
A ________ (pulse/wave) is a disturbance which is sudden and lasts for a short duration of time.
Q 28.
Fill in the blanks :
In a __________ wave the particles of the medium oscillate in a direction perpendicular to the direction in which the wave propagates.
Q 29.
Fill in the blanks :
The distance between two consecutive compressions or two consecutive rarefactions is called the ______________.
Q 30.
What is a mechanical wave?
Q 31.
Why sound waves are called mechanical waves?
Q 32.
How are the wavelength and frequency of a sound wave related to its speed?
Q 33.
A sound wave travels at a speed of 339 ms
–1. If its wavelength is 1.5 cm, what is the frequency of the wave?
Q 34.
What is infrasonic? Give an example.
Q 35.
A child hears an echo from a cliff 4 s after the sound of a pwerful cracker is produced.How far away is the cliff from the child ? (Take speed of sound in air as 340 m/s)
Q 36.
An engine is approaching a hill at constant speed.When it is at a distance of 0.9 km,it blows a whisde,whose echo is heard by the driver after 5 s.If the speed of sound is 340 m/s,calculate the speed of the engine.
Q 37.
Guess which has a higher pitch : a guitar or a car horn ?
Q 38.
What is sound and how is it produced ?
Q 39.
The frequency of a source of sound is 100 Hz.How many times does it vibrate in a minute ?
Q 41.
What is the minimum distance of the obstacle from the source of sound for hearing distinct echo ?
Q 42.
What is sound ? Discuss the method of its production.
Q 43.
Obtain a relation between speed,frequency and wavelength of a wave.
Q 44.
What do you mean by reverberation and reverberation time ? How is reverberation controlled ?
Q 45.
Deaf people can be made to dance to music.Explain how ?
Q 46.
Fill in the blanks :
If a body repeats its motion, within fix interval of time, along a certain path, about a fixed point, it is said to have ____________.
Q 47.
Fill in the blanks :
Number of oscillations completed by the oscillator in one second is known as ___________.
Q 48.
Fill in the blanks :
Sound, compressional waves in springs are examples of _____________.
Q 49.
Fill in the blanks :
Loudness of sound is measured in ___________.
Q 50.
What type of waves can travel in vacuum? Give example(s).
