1. The speed of a transverse wave on a stretched string depends on:
a) Length of string
b) Tension and mass per unit length
c) Amplitude
d) Frequency
Answer: b
2. In standing waves, points of zero displacement are called:
a) Antinodes
b) Nodes
c) Loops
d) Crests
Answer: b
3. Wave number k is related to wavelength λ as:
a) k = λ/2π
b) k = π/λ
c) k = 2π/λ
d) k = 1/λ
Answer: c
4. Relationship between wave speed v, frequency f and wavelength λ is:
a) v = f/λ
b) v = f × λ
c) v = λ / f
d) v = f² λ
Answer: b
5. Constructive interference occurs when phase difference is:
a) π
b) π/2
c) 0 or 2πn
d) Random
Answer: c
6. Beat frequency produced by two tones f1 and f2 is:
a) f1 + f2
b) |f1 − f2|
c) f1 × f2
d) (f1 + f2)/2
Answer: b
7. The Doppler effect changes which property of a wave as observer/source move?
a) Amplitude
b) Frequency
c) Phase only
d) Power
Answer: b
8. For a string fixed at both ends, allowed wavelengths are λ_n = 2L/n. n is:
a) Any real
b) Positive integer (harmonic number)
c) Only even integers
d) Only odd integers
Answer: b
9. Fundamental frequency of an open-open pipe of length L is f1 = v/2L. True or false?
a) True
b) False
c) True only if closed at one end
d) Depends on temperature only
Answer: a
10. Intensity of a wave is proportional to:
a) Amplitude
b) Amplitude²
c) Frequency
d) Wavelength
Answer: b
11. Phase velocity v_p is defined as:
a) ω/k
b) k/ω
c) dω/dk
d) f × λ
Answer: a
12. Group velocity (energy velocity) equals:
a) ω/k
b) dω/dk
c) f/λ
d) k/ω
Answer: b
13. Dispersion means:
a) Phase velocity independent of frequency
b) Phase velocity depends on frequency
c) No energy transport
d) Waves vanish
Answer: b
14. Reflection at a fixed end causes:
a) No phase change
b) Phase inversion (π)
c) Amplitude zero
d) Frequency change
Answer: b
15. Huygens' principle states:
a) Every point on a wavefront acts as source of secondary wavelets
b) Waves travel in straight rays only
c) Energy is destroyed at nodes
d) Interference is impossible
Answer: a
16. The acoustic impedance Z = ρ v (ρ = density, v = speed). True or false?
a) True
b) False
c) Only in vacuum
d) Only for electromagnetic waves
Answer: a
17. In a closed (one end) pipe, the allowed harmonics are:
a) All integer harmonics
b) Only even harmonics
c) Only odd harmonics
d) No harmonics
Answer: c
18. Which waves do not require a material medium?
a) Sound waves
b) Water waves
c) Electromagnetic waves
d) Seismic waves
Answer: c
19. The relation for speed of sound in ideal gas: v = √(γRT/M). This v depends on:
a) Pressure only
b) Temperature and molecular mass
c) Amplitude
d) Frequency
Answer: b
20. Echo is heard because of:
a) Diffraction
b) Reflection of sound from distant surface
c) Refraction
d) Interference
Answer: b
21. Beats can be used to measure:
a) Amplitude exactly
b) Small frequency differences
c) Wave speed
d) Wavelength directly
Answer: b
22. Node to next node distance in standing wave is:
Answer: b
23. The Rayleigh criterion relates to:
a) Resolving power (diffraction limit)
b) Beats frequency
c) Acoustic impedance
d) Wave attenuation
Answer: a
24. Evanescent waves occur when:
a) Frequency above cutoff
b) Frequency below cutoff (in waveguides)
c) In free space only
d) At resonance always
Answer: b
25. Energy density of a harmonic wave ∝:
a) Amplitude
b) Amplitude²
c) Frequency
d) Wavelength
Answer: b
26. The phenomenon of diffraction is most pronounced when obstacle size is:
a) Much larger than λ
b) Comparable to λ
c) Much smaller than λ
d) Irrelevant
Answer: b
27. In an open-closed tube, fundamental wavelength λ1 = 4L. The next harmonic present is:
a) 2nd harmonic (2×f1)
b) 3rd harmonic (3×f1)
c) 4th harmonic
d) None
Answer: b (only odd harmonics)
28. For transverse waves on string, higher tension results in:
a) Lower speed
b) Higher speed
c) No change
d) Amplitude change only
Answer: b
29. Phase difference between displacement and velocity in SHM is:
Answer: b
30. Sound intensity level increase by 10 dB means intensity is:
a) Doubled
b) Ten times
c) Square-root
d) Unchanged
Answer: b
31. The node in displacement in a sound standing wave corresponds to:
a) Pressure node
b) Pressure antinode
c) Both node and antinode
d) No pressure variation
Answer: b
32. In wave refraction, frequency when crossing boundary:
a) Changes
b) Remains same
c) Doubles
d) Halves
Answer: b
33. Phase difference between two points separated by distance x is:
a) 2πx/λ
b) 2πλ/x
c) x/λ
d) πx/λ
Answer: a
34. For water waves in shallow water (depth d ≪ λ), speed ≈:
a) √(gλ/2π)
b) √(gd)
c) Independent of depth
d) Proportional to frequency
Answer: b
35. Parametric resonance typical excitation frequency is:
a) Natural frequency
b) Twice natural frequency (or multiples)
c) Zero
d) Random
Answer: b
36. Solitons arise due to balance between:
a) Dispersion and dissipation
b) Dispersion and nonlinearity
c) Nonlinearity only
d) External forcing
Answer: b
37. Ultrasonic waves are used in medical imaging because they have:
a) Longer wavelength for deep penetration
b) Shorter wavelength for higher resolution
c) Audible frequency
d) No reflection
Answer: b
38. Acoustic impedance mismatch at boundary causes:
a) Complete transmission
b) Partial reflection and partial transmission
c) Only absorption
d) No effect
Answer: b
39. Rayleigh criterion is used to determine:
a) Beat frequency
b) Diffraction-limited resolution
c) Wave speed in medium
d) Standing wave nodes
Answer: b
40. Waveguide cutoff frequency means below cutoff the wave is:
a) Propagating
b) Evanescent (decays)
c) Amplified
d) Converted to sound
Answer: b
41. When two harmonic waves of equal amplitude are exactly out of phase (π), resultant amplitude is:
a) 2A
b) 0 (complete cancellation)
c) A
d) √2 A
Answer: b
42. Timbre of a musical note depends primarily on:
a) Fundamental frequency only
b) Relative amplitudes of harmonics (overtones)
c) Loudness only
d) Phase only
Answer: b
43. The short pulse spreading in dispersive medium occurs because:
a) All frequency components travel with same phase velocity
b) Different frequency components travel at different velocities
c) Energy is lost only
d) Wavelength increases
Answer: b
44. A 10 dB increase in sound level corresponds to what factor increase in intensity?
Answer: c
45. Inverse-square law for a point source means intensity ∝:
a) r
b) 1/r
c) 1/r²
d) r²
Answer: c
46. Which of these is a transverse mechanical wave?
a) Sound in air
b) Water surface waves (partially)
c) Compression waves in solids
d) Heat conduction
Answer: b
47. The most probable speed in Maxwell distribution relates to temperature as v_mp =:
a) √(kT/m)
b) √(2kT/m)
c) √(3kT/m)
d) √(kT/2m)
Answer: b
48. In acoustics, directivity of a source changes strongly when source size is comparable to:
a) Wavelength
b) Frequency
c) Amplitude
d) Intensity
Answer: a
49. When two slightly different frequencies are superposed, amplitude modulation rate equals:
a) Sum of frequencies
b) Difference of frequencies
c) Product of frequencies
d) Average of frequencies
Answer: b
50. Energy transported by a harmonic wave is proportional to:
a) Amplitude
b) Amplitude²
c) √(Amplitude)
d) ln(Amplitude)
Answer: b