Unit – 11 : Waves (Multiple Choice Questions)

1. A student tunes his guitar by striking a 120 Hz tuning fork and plays the 4th string. The amplitude oscillates 3 times per second. The frequency of the string is

a) 130 Hz
b) 117 Hz
c) 110 Hz
d) 120 Hz
Answer: b)

2. A transverse wave moves from medium A to B. In A, $v=500$ m s$^{-1}$, $\lambda=5$ m. In B, $v=600$ m s$^{-1}$. Frequency and wavelength in B are

a) 120 Hz, 5 m
b) 100 Hz, 5 m
c) 120 Hz, 6 m
d) 100 Hz, 6 m
Answer: d)

3. Among six harmonics below 1000 Hz, only four are 300, 600, 750 and 900 Hz. The missing harmonics are

a) 100 Hz, 150 Hz
b) 150 Hz, 450 Hz
c) 450 Hz, 700 Hz
d) 700 Hz, 800 Hz
Answer: b)

4. Match the following:

AB
(1) Quality(A) Intensity
(2) Pitch(B) Waveform
(3) Loudness(C) Frequency
a) (B), (C), (A)
b) (C), (A), (B)
c) (A), (B), (C)
d) (B), (A), (C)
Answer: a)

5. Travelling wave equation is $y=0.03\sin(450t-9x)$. Linear density is $5\,g\,m^{-1}$. Tension is

a) 5 N
b) 12.5 N
c) 7.5 N
d) 10 N
Answer: b)

6. A sound wave of frequency 5000 Hz travels in air and then water. The ratio of wavelengths is

a) 4.30
b) 0.23
c) 5.30
d) 1.23
Answer: a)

7. First echo at $t_1$ and second echo at $t_2$. Distance between hills is

a) $\dfrac{v(t_1-t_2)}{2}$
b) $\dfrac{v(t_1+t_2)}{2}$
c) $v(t_1+t_2)$
d) $\dfrac{v(t_1+t_2)}{2}$
Answer: d)

8. Closed pipe resonates at 83 Hz. Length of air column is

a) 1.5 m
b) 0.5 m
c) 1.0 m
d) 2.0 m
Answer: c)

9. $y=2\times10^{-3}\sin(300t-2x+\pi/4)$. Speed of wave is

a) 150 m s$^{-1}$
b) 300 m s$^{-1}$
c) 450 m s$^{-1}$
d) 600 m s$^{-1}$
Answer: a)

10. Beat frequency = 10 Hz, higher pitch = 360 Hz. Ratio $x:y$ is

a) 36:35
b) 35:36
c) 1:1
d) 1:2
Answer: a)

11. Which represents a wave?

a) $(x-vt)^3$
b) $x(x+vt)$
c) $\dfrac1{x-vt}$
d) $\sin(x+vt)$
Answer: d)

12. Maximum Doppler frequency heard is

a) 2.027 kHz
b) 1.974 kHz
c) 9.74 kHz
d) 1.011 kHz
Answer: a)

13. Wave shifts from $y=\frac1{1+x^2}$ to $y=\frac1{1+(x-2)^2}$ in 2 s. Velocity is

a) 0.5 m s$^{-1}$
b) 1.0 m s$^{-1}$
c) 1.5 m s$^{-1}$
d) 2.0 m s$^{-1}$
Answer: b)

14. A transverse wave travels in a hanging rope. Correct variation of speed $v$ with height $h$ is

v vs h graph options
a) (a)
b) (b)
c) (c)
d) (d)
Answer: d)

15. Closed pipe (1st harmonic) and open pipe (3rd harmonic) resonate. Ratio of lengths is

a) $\frac{8}{3}$
b) $\frac{3}{8}$
c) $\frac{1}{6}$
d) $\frac{1}{3}$
Answer: c)