CBSE Class 11 Physics Wave Motion Objective Questions

1. The displacement of a wave is represented by y = 0.25 × 10^–3 sin (500 t – 0.05 x) where all the quantities are in their S.I. unit. The maximum particle velocity of the medium is .
(a) 0.5 ms^–1 (b) 0.75 ms^–1 (c) 0.125 ms^–1 (d) 0.150 ms^–1

2. If the ratio of the amplitudes of two interfering beams be 2 : 3, the ratio of the minimum and maximum intensities of sound would be
(a) 4 : 9 (b) √2 :√3 (c) 1 : 5 (d) 1 : 25

3. In the interference of waves from two sources of intensities I0 and 4I0, the intensity at a point where the phase difference is π is
(a) 5I0 (b) 3I0 (c) 2I0 (d) I0

4. In stationary waves
(a) pressure nodes and antinodes coincide with displacement nodes and antinodes
(b) velocity nodes and antinodes coincide with displacement nodes and antinodes
(c) pressure nodes and antinodes coincide with velocity nodes and antinodes
(d) none of these

5. A transverse wave is described by the equation y = y0 sin 2π(ft –x/λ) The maximum particle velocity is equal to four times the wave velocity if
(a) λ = πy0 /4 (b) λ = πy0/2  (c) λ = πy0 (d) λ = 2πy0

6. The fundamental frequency of a vibrating organ pipe is 200 Hz.
(a) The first overtone is 400 Hz (b) The first overtone may be 400 Hz
(c) The first overtone may be 600 Hz (d) 600 Hz is an overtone.

7. In the equation y = a sin k(x – pt), wher ,k = 2/λ the speed of the wave is

(a) p (b) kp (c) k/p (d) p/k

8. The speed of sound through a gaseous medium bears a constant ratio with the rms speed of its molecules that constant ratio is
(a) γ/3  (b) γ – 1 (c) 2γ/3  (d) γ

9. The temperature at which the velocity of sound is double its velocity at 0°C is
(a) 546° C (b) 819°C (c) 1092° C (d) 273° C

10. In the fourth harmonic of an open organ pipe, there are
(a) 2N, 3 A (b) 3N, 4A (c) 4N, 5A (d) 5N, 4A

11. The length of an open pipe is 25 cm and the velocity of sound in air is 350 ms^–1. The frequency in Hz of
the second harmonic of the pipe is
(a) 350 (b) 700 (c) 1050 (d) 1400

12. A stretched string vibrates with a frequency of 30 Hz in its fundamental mode when the supports are 60 cm apart. The velocity of transverse waves in the string is
(a) 9 ms^–1 (b) 18 9 ms^–1 (c) 36 ms^–1 (d) 72 ms^–1

13. A string B has twice the length, twice the diameter, twice the tension and twice the density of another string A. Which of the following alternatives expresses the relation between the frequencies of A and B?
(a) n_B = 4n_A (b) n_A = 4n_B (c) n_A = 2n_B (d) 2n_B = n_A

14. The equation y = A sin²(kx– ωt) represents a wave motion with
(a) amplitude A frequency ω/2π (b) amplitude A/2, frequency ω/π
(c) amplitude 2A, frequency ω/4π (d) does not represent a wave motion.

15. A wave pulse, travelling on a two-piece string, gets partially reflected and partially transmitted at the junction. The reflected wave is inverted in shape as compared to the incident one. If the incident wave has wavelength λ and the transmitted wave λ´,
(a) λ´ > λ (b) λ´ = λ (c) λ´ < λ (d) nothing can be said about the relation of λ and λ´

16. Two waves represented by y = a sin (ωt –kx) and y = a cos (ωt –kx) are superposed. The resultantwave will have an amplitude
(a) a (b) √2 a (c) 2 a (d) 0

17. Two wires A and B having identical geometrical construction, are stretched from their natural length by equal amount. The Young’s modulus of the wires are YA and YB whereas the densities are ρA and ρB. It is given that YA > YB and ρA > ρB. A transverse signal started at one end takes a time t1 to reach the other end for A and t2 for B.
(a) t1 < t2 (b) t1 = t2 (c) t1 > t2 (d) The information is insufficient to find the relation between t1 and t2

18. Two sine waves travel in the same direction in a medium. The amplitude of each wave is A and the phase difference between the two waves is 120°. The resultant amplitude will be
(a) A (b) 2A (c) 4A (d) √2A