Waves — Previous-Year Questions

Q1. Which is NOT a transverse wave?

Q2. A wave on a string has T = 100 N, μ = 0.04 kg/m. Wave speed:

Q3. If tension is quadrupled, wave speed on a string:

Q4. y = 5·sin(10x − 200t). Wavelength and frequency:

Q5. Polarisation is a property of:

Q1. Sound in air at 20°C is approximately:

Q2. If air temperature rises from 0°C to 100°C, sound speed:

Q3. Why do P-waves travel through Earth's outer core but S-waves don't?

Q4. Sound in water (B = 2.2×10⁹ Pa, ρ = 1000 kg/m³):

Q5. Longitudinal waves can be polarised:

Q1. When a wave enters a new medium:

Q2. Wave on string fixed at one end — reflected wave at fixed end is:

Q3. Two waves of equal amplitude in PHASE superpose. Resultant amplitude:

Q4. Diffraction of waves becomes noticeable when:

Q5. Energy transported by a wave is proportional to:

Q1. Sound of 440 Hz in air at v = 343 m/s. Wavelength:

Q2. If frequency is doubled (same medium), wavelength:

Q3. A wave has v = 200 m/s and λ = 0.5 m. Frequency:

Q4. When sound enters water from air, λ:

Q5. Period of a 2 kHz wave is:

Q1. A string has T = 64 N, μ = 0.01 kg/m. Wave speed:

Q2. If tension is doubled and μ kept same, wave speed:

Q3. Two strings: μ₁ = 0.02 kg/m, μ₂ = 0.08 kg/m (same T). Speed ratio v₁/v₂:

Q4. Power transmitted by a sinusoidal wave on a string:

Q5. Thicker guitar strings produce LOWER notes because:

Q1. Two coherent waves of equal amplitude A interfere constructively. Resultant amplitude:

Q2. Two coherent waves of equal intensity I₀ destructively interfere. Resultant intensity:

Q3. Coherent sources are required for:

Q4. Two equally intense sources have intensities I_max/I_min ratio:

Q5. Path difference for first bright fringe (constructive) from a 600 nm source:

Q1. Two strings vibrate at 256 Hz and 260 Hz. Beat frequency:

Q2. When tuning two musical strings to the same pitch, you listen for:

Q3. Two tuning forks at 256 Hz and 260 Hz played together. How many beats heard in 5 seconds?

Q4. When the two source frequencies become EQUAL (f₁ = f₂):

Q5. Above ~15 Hz of beat frequency:

Q1. Distance between adjacent nodes in a standing wave is:

Q2. Standing wave on a string of length L fixed at both ends. Fundamental wavelength:

Q3. A standing wave has nodes at 0, 2, 4 cm. Wavelength:

Q4. Energy transported by a perfect standing wave:

Q5. A standing wave is formed by:

Q1. Distance between adjacent node and antinode is:

Q2. String of length 1 m fixed at both ends. Fundamental wavelength:

Q3. A closed organ pipe (closed at one end) of length 0.5 m. Fundamental wavelength:

Q4. A pipe closed at one end can produce:

Q5. In a standing wave, ANTINODES are points of:

Q1. Sound speed at 27°C is 348 m/s. At 127°C (400 K):

Q2. Sound cannot propagate in:

Q3. Threshold of hearing intensity:

Q4. Sound speed in air depends on:

Q5. Why is sound speed in steel much greater than in air?

Q1. Sound speed in air (γ = 1.4, M = 0.029 kg/mol, T = 300 K):

Q2. Helium sound speed vs air (same T):

Q3. If gas temperature doubles, sound speed:

Q4. Sound speed in pure water at 20°C is approximately:

Q5. Pressure does NOT affect sound speed in an ideal gas because:

Q1. An ambulance siren at 1000 Hz approaches a stationary observer at 30 m/s. Sound speed 330 m/s. Apparent frequency:

Q2. If the ambulance is RECEDING at 30 m/s instead:

Q3. If a source moves AT the speed of sound:

Q4. Police radar uses Doppler effect on:

Q5. Mach angle of an aircraft at Mach 2 (v_s = 2v):

Q1. Observer approaches stationary 500 Hz source at 40 m/s. v_sound = 340 m/s. f':

Q2. If observer RECEDES at 40 m/s instead:

Q3. Doppler effect formula for moving observer vs moving source:

Q4. Both source and observer move TOWARD each other at v_s = v_o = 20 m/s. v = 340 m/s, f = 1000 Hz. f':

Q5. If both source and observer move with the SAME velocity (e.g., car following another), Doppler shift is:

Q1. Source moves at 20 m/s toward observer, who moves at 10 m/s toward source. f = 1000 Hz, v = 330 m/s. f':

Q2. Both source and observer recede from each other at 30 m/s. f = 500 Hz, v = 340 m/s. f':

Q3. Source and observer move with the SAME velocity in the same direction. Doppler shift:

Q4. Maximum Doppler shift up occurs when:

Q5. Doppler shift formula for sound is approximately:

Q1. String of length 1 m, v = 200 m/s. Frequency of 3rd harmonic:

Q2. If string tension is quadrupled (same L, μ), fundamental frequency:

Q3. Stretched string allows which harmonics?

Q4. If we shorten the string by half (same T, μ), fundamental f:

Q5. Why do different stringed instruments sound different even at the same pitch?

Q1. Open organ pipe of length 1 m, v = 340 m/s. Fundamental frequency:

Q2. Same pipe but closed at one end. Fundamental frequency:

Q3. A closed organ pipe produces:

Q4. Frequency of 3rd harmonic of a closed pipe vs fundamental:

Q5. Why is closed-pipe fundamental HALF the open-pipe fundamental (same L)?

Q1. Power transmitted by a wave is proportional to:

Q2. Sound intensity at 10 m from a point source is I. At 20 m:

Q3. If amplitude doubles and frequency doubles, power increases by:

Q4. Decibel scale is:

Q5. Doubling sound intensity changes dB level by:

Q1. Phase difference for path difference of λ/4:

Q2. Two coherent sources differ in phase by π. Their waves at the same point:

Q3. If two sources are in phase and observe Δx = 3λ/2 at a point. Result:

Q4. Phase difference of π corresponds to path difference of:

Q5. Two SHMs of equal A with phase difference π/2. Superposition amplitude: