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Syllabus
7. a. Electromagnetic waves directed towards a newly discovered comet are received back in an interval of 20,400 minute. How far is the comet from earth ? [State the necessary assumption used]
2. Calculate the minimum distance in air required between the source of sound and the obstacle to hear an echo. Take speed on sound in air = 350 m s-1. Ans. 17.5 m.
3. What should be the minimum distance between resource and reflector in water so that echo is heard distinctly ?
( The speed of sound in water = 1400 m s-1). Ans. 70 m.
Q9. A person standing between the two vertical cliff, produces a sound. TWO successive echoes are heard at 4 s and 6 s, Calculate the distance the cliff (Speed Of sound in air =320 ms-1 )
[Hint : First echo Will he heard from the nearest cliff and the second echo from the farther cliff.]
Q10. A man fires a gun and hears its echo after 5 s. The man then moves 310 m towards the hill and
fires his gun again. This time be hears the echo after 3 s. Calculate the speed Of sound.
Q11. On sending an ultrasonic wave from a ship toward the bottom Of a sea, the time interval between sending the wave and receiving it back is found to be 1.5 s .If the velocity of wave in sea water is 1400 ms-1. Find the depth of the sea
Q(a). Two simple pendulums A and B of different lengths are suspended from the same string as shown in the figure. When A is displaced from its mean position and is let go, it is found that B also starts vibrating.
1. Name the phenomenon that is responsible for the vibrations of B.
ii. Does the frequency of the vibration of B depend on its own length or one the frequency of the vibration of A ?
iii. What would happen to the amplitude of the vibration of B if its string length was made equal to the string length of A?
iv. Name the phenomenon which occurs when the string length of B is made equal to the string length of A.
(i)- If the person wants to hear the echo 0.5 s earlier, then how much distance should he move, toward or away from the cliff?
(ii)- Another person stands behind this person, in the same line with him and the cliff, at a distance of 170 m and fires a gun in the air. What are the consecutive intervals of time at which the first person hears two sounds?
(iii)- If the speed of sound changes to 350 m/s then how much distance should the person move towards or away from the cliff, in order to hear the echo in the same time? (i.e. in 3 s)?
In the FORCED VIBRATIONS,the vibration of the body are not in phase with the external periodic force.
1. The wavelength of waves produced on the surface of water is 20 cm. If the wave velocity is 24 m s-1,
Calculate : (i) The number of waves produced in one second, and (ii) The time in which one wave is produced. Ans. (i) 120 (ii) 8.3 x 10-3 s
Question 7
(a). (i) Name type of waves which are used for sound ranging.
(ii) Why are these waves mentioned in (i) above, not audible to us?
(iii) Give one use of sound ranging.
How does it happen?
Please explain it, meritnation and my colleagues....
.......
1. Amplitude
2. Wave form
Q.2. The displacement y of a wave travelling in by x-direction is given by where x is expressed in meters and t in seconds. The speed of the wave motion (in m) is
(a) 400
(b) 800
(c) 1200
(d) 200