Two identical loudspeakers separated by 2 m emit sound of frequency 340 Hz in phase. If the speed of sound is 340 m/s, constructive interference occurs at:
Answer: D
Constructive interference occurs when path difference = nλ. λ = v/f = 340340 = 1 m, so path difference = 0, 1 m, 2 m, etc.
Q.63Medium
A pipe closed at one end has its fundamental frequency at 200 Hz. The next higher harmonic that can be produced is:
Answer: B
In a pipe closed at one end, only odd harmonics are produced: f, 3f, 5f, etc. Next higher = 3 × 200 = 600 Hz
Q.64Easy
A longitudinal wave has frequency 50 Hz and wavelength 8 m. The wave velocity is:
Answer: A
v = fλ = 50 × 8 = 400 m/s
Q.65Medium
A wave pulse travels along a rope. When it reaches a fixed end, the reflected pulse is:
Answer: B
At a fixed end, the reflected wave undergoes a phase change of 180° (or π radians) due to the fixed boundary condition
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Q.66Easy
Standing waves are formed on a string by superposition of two waves traveling in opposite directions with:
Answer: C
Standing waves form from superposition of two waves with equal amplitude, frequency, and wavelength traveling in opposite directions
Q.67Medium
A progressive wave is represented as y = 2sin(100πt - πx/2). The phase difference between particles at x = 1 m and x = 3 m is:
Intensity I ∝ A²f² (or I ∝ A²ω²), both amplitude and frequency squared affect intensity
Q.69Easy
A person hears sound from two sources with frequencies 400 Hz and 404 Hz. The beat frequency heard is:
Answer: B
Beat frequency = |f₁ - f₂| = |400 - 404| = 4 Hz
Q.70Medium
A wave undergoes refraction when passing from one medium to another. Which quantity remains constant?
Answer: C
During refraction, frequency remains constant as it depends on the source. Wavelength and velocity change due to change in medium properties
Q.71Medium
A string vibrates with 4 antinodes forming a standing wave pattern. The number of nodes (excluding ends) is:
Answer: A
For 4 antinodes (loops), there are 3 internal nodes. Pattern: node-antinode-node-antinode-node-antinode-node-antinode-node
Q.72Easy
The Doppler effect is observed when:
Answer: B
Doppler effect occurs due to relative motion between source and observer, causing apparent frequency change
Q.73Medium
A standing wave on a string has nodes at x = 0 and x = 2 m. The wavelength is:
Answer: C
Distance between two consecutive nodes = λ/2. If nodes are at 0 and 2 m, then λ/2 = 2, so λ = 4 m
Q.74Hard
A tuning fork of frequency 512 Hz is vibrating above a resonance tube filled with water. As water level is lowered, resonance first occurs at length 16 cm. The speed of sound is:
Answer: A
First resonance in pipe closed at one end: L₁ = λ/4. So λ/4 = 0.16 m, λ = 0.64 m. v = fλ = 512 × 0.64 = 327.68 ≈ 328 m/s
Q.75Medium
Two sound waves have frequencies 256 Hz and 260 Hz. If they produce 4 beats per second, the beat frequency matches when:
Answer: B
Beat frequency = |f₁ - f₂| = 4 Hz only when waves overlap in the same region of space
Q.76Hard
A wave pulse on a rope travels from a denser to a lighter medium (from thin to thick rope). The reflected pulse:
Answer: B
At boundary from denser to less dense medium, reflected pulse is NOT inverted but has smaller amplitude due to partial reflection
Q.77Easy
A wave is traveling through a medium with velocity v = 340 m/s. If the wavelength is 0.85 m, what is the frequency of the wave?
Answer: A
Using v = fλ, f = v/λ = 0340.85 = 400 Hz
Q.78Easy
Which of the following correctly represents the relationship between wave velocity, frequency, and wavelength?
Answer: B
The fundamental wave equation is v = fλ, where v is velocity, f is frequency, and λ is wavelength
Q.79Easy
A guitar string of length 0.6 m is vibrating in its third harmonic. How many antinodes are present on the string?
Answer: C
In the nth harmonic, the number of antinodes equals n. For the third harmonic (n=3), there are 3 antinodes
Q.80Easy
The amplitude of a wave is doubled. How does this affect the intensity of the wave?
Answer: B
Intensity is proportional to the square of amplitude (I ∝ A²). When A becomes 2A, I becomes 4I
