1. Calculate the stress in tight wire of material whose Young's modulus is 19.6 × 1011 dyne / cm2. So that the speed of longitudinal waves is ten times the speed of transverse waves.
Ans: 19.6 × 109 dyne/cm2
Hint:
2. The equation of a travelling wave y = 60 cos (1800t - 6x) where y is in microns, t is in seconds, x is in meters. The ratio of maximum particle velocity to the wave velocity of wave propagation is
Ans: 3.6 × 10-4
Hint:
3. The ratio of intensity of wave and energy density gives
Ans: velocity
Hint:
4. Assertion (A): Solids can support both longitudinal and transverse waves, but only longitudinal waves can propagate in gases.
Reason (R): Solids possess two types of elasticity.
Ans: Both A & R are true but R is not correct explanation of 'A'.
Hint: Conceptual
5. In a medium in which a transverse progressive wave is travelling, the phase difference between two points with a separation of 1.25 cm is (π/4). If frequency of wave is 1000 Hz. Its velocity will be
Ans:100 m/s
6. A 40 cm long brass rod is dropped, one end first on to a hard floor, but is caught before it topless over. 3 KHz tone is produced due to impact. Speed of sound in brass is
Ans: 2.4 × 103 m/s
Hint: The brass rod is 'open' at both sides So,
7. The displacement 'y' of a particle is given by 
sin (1000 t). This expression may be considered to be a result of super position of ----- waves.
Ans:4
Hint:
8. A rope of length 'l' and mass 'm' hangs freely from the ceiling. The velocity of transverse wave as a function of position x along the rope is proportional to
Ans: x1/2
Hint:
9. An object of specific gravity 'ρP' is hung from a thin steel wire. The fundamental frequency for transverse standing waves in the wire is 300 Hz. The object is immerse in water so that one half of its volume is submerged. The new fundamental frequency in Hz is
Ans: 
Hint:
10. A copper wire is held at two ends by rigid supports. At 40°C the wire is just taut with negligible tension. The speed of transverse wave in the wire at 10°oC is (α = 7 × 10-6/ °C, Y = 2.1 × 1010 N/m2, density = 9000 kg/m3)
Ans: 70 m/s
Hints:
11. The diameter of a stretched string is increased by 3% keeping the other parameters constant then the velocity is
Ans: 3% decreases
Hint:
12. A number of tuning forks are arranged in the order of increasing frequency and any two successive tuning forks produce 4 beats per second when sounded together. If the last tuning fork has a frequency octave higher than that of is 256 Hz, then no. of tuning forks are
Ans: 65
Hint:
Let the frequency of first fork be 'n' frequency o last fork = 2n, the frequencies are thus, n, n+4, n+8....2n
13. A tuning fork of frequency 340 Hz is allowed to vibrate just above a 120 cm high tube. Water being slowly filled in resonance will be (given C = 340 m/s)
Ans: 45 cm
Hint:
Max length of air column is 75 cm.
Max height of water column = 120 - 75 = 45 cm
14. Two organ pipes, both closed at one end, have lengths l and l + 
l. Neglect end correction. If velocity of sound in air is V. Then no. of beats/sec is
Ans: 
Hint:
15. Two waves having intensities I and 9I produce interference. If the resultant intensity at a point is 7 I. What is the phase difference between two waves?
Ans: 120° degrees
Hint:
16. Two whistles A and B produce notes of frequencies 660 Hz and 596 Hz respectively. There is a listener at the mid point of line joining them. Both the whistle B and listener start moving with speed of 30 m/s away from whistle A. If the speed of sound is 330 m/s. How many beats will be heard by the listener?
Ans: 4
Hint:
17. A magnet of magnetic moment M is bent with lengths in the ratio x : y. Each part is making an angle 90o with each other. Then new magnetic moment is
Ans: 
Hint:
18. A bar magnet of magnetic moment M is bent in the form of an arc which makes an angle 60°. The percentage change in the magnetic moment is
Ans: 4.5% decreases
Hints:
19. Two bar magnets are placed in a vibration magnetometer and allowed to vibrate. They make 15 oscillations per minute. When their similar poles are on the same side. While they make 20 oscillations per min. When their opposite poles lie on the same side. The ratio of magnetic moments is
Ans: 25 : 7
Hint: 
