Physics is where JEE ranks are usually won or lost, since a single conceptual slip changes the whole answer. Questions here span mechanics, rotational motion, thermodynamics, waves and oscillations, electrostatics, current electricity, magnetism, optics, and modern physics. Numerical problems carry full derivations so you can see which step you skipped, not just which option was right.
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
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
