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1
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What do you mean by echo and state 2 conditions for an echo to be heard distinctly?
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2
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State the application of echo by a bat, dolphin, fisherman, etc.
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3
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What is SONAR? State the principle on which it is based.
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4
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Numerical sum based on:
v= d/t (when echo is not mentioned in the
question)
v= 2d/t (when echo is mentioned in the
question)
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5
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A man standing 25 m away from a wall produces a sound and receives the reflected sound:
- Calculate the time after which he receives the reflected sound, if the speed of sound in air is 350 m/s.
- Will the man be able to hear a distinct echo? Give a reason.
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6
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A man standing in front of a cliff fires a gun. An echo is heard after 3 s. On moving 80 m closer to the cliff, he again fires a gun and hears an echo after 2.5 s. Calculate:
(a) The distance of man from the cliff to his initial position.
(b) The speed of sound.
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7
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What do you mean by natural vibrations of a body? Draw a graph between displacement and time of a body executing the natural vibration. State one condition for a body to execute the natural vibration.
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8
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State the factors on which the frequency depends for the following:
- Stringed instruments {Freq a (1/1) }
- Bob of a simple pendulum
- Load suspended from a spring
- Air column in a flute
- Organ pipe open at both end (1:2:3)
- Organ pipe with one end closed (1:3:5)
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9
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What is the purpose of strings of different thickness in a stringed instrument?
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10
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Write down the differences between free and forced vibrations with corresponding examples. Also draw a sketch showing the displacement against time for a body executing the damped vibrations.
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11
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What is meant by resonance? What is the condition necessary for resonance to take place?
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12
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Write down the application of resonance in the case of:
- Tuning fork of same frequency
- Resonant vibrations of pendulum of same length suspended from the same elastic support.
- Air column when a long cylindrical tube is connected with a cylindrical vessel which acts as a reservoir.
- Machine parts when at a certain speed of the vehicle that particular part of the frame starts vibrating vigorously.
- Stretched string and sound box of musical instruments and sonometer.
- Troops cross a suspension bridge
- Test tubes of the same height which are filled with water up to different heights.
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13
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Give comparison of sound on the basis of 3 characteristics, i.e. loudness, pitch and quality and their subjective nature.
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14
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Define loudness. Name the corresponding measurable quantity.
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15
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Mention the factors of loudness and intensity.
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16
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The bells of a temple are big in size. Why?
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17
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What is the unit for sound level?
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18
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What is the unit of loudness?
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19
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Define Pitch. Give its measurable quantity.
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20
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The ratio of amplitude of 2 waves having the same pitch is 3:4. What is the ratio of their:
- Loudness (directly proportional to a square)
- Frequency
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21
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How is it possible to detect the filling of a bottle under a water tap by hearing the sound at a distance?
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22
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Define quality of sound.
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23
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Which characteristic of sound makes it possible to recognize a person from his voice without seeing him?
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24
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Differentiate between musical note and a noise.
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25
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Technical name of the musical instrument Flute is an organ pipe. If the pipe is open at one end (closed pipe), then its fundamental frequency is V/4| and if it is open at both ends then its fundamental frequency is V/2I. What will be the impact on quality of sound?
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