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.
A wave travels through two media. In medium 1, its speed is 400 m/s and wavelength is 2 m. In medium 2, the speed is 600 m/s. The wavelength in medium 2 is:
Answer: B
Frequency remains constant. f = v₁/λ₁ = 2400 = 200 Hz. In medium 2: λ₂ = v₂/f = 200600 = 3 m
Q.822Easy
The intensity of a sound wave is inversely proportional to which of the following?
Answer: B
For a point source, intensity I ∝ 1/r². This is the inverse square law for spherical waves
Q.823Easy
A harmonic wave travels along a string with amplitude 2 cm and wavelength 40 cm. If the wave completes 10 oscillations in 5 seconds, what is the wave velocity?
Answer: A
Frequency f = 510 = 2 Hz, λ = 40 cm, v = fλ = 2 × 40 = 80 cm/s
Q.824Easy
The equation of a wave is y = 0.06 sin(100t - 8x), where x and y are in meters and t is in seconds. The wavelength is:
Answer: A
From equation, wave number k = 8 rad/m. λ = 2π/k = 2π/8 = 0.785 m
Q.825Easy
Two waves of equal amplitude and slightly different frequencies are superposed. The resulting pattern is called:
Answer: B
When two waves of slightly different frequencies interfere, alternating constructive and destructive interference produces beats with beat frequency = |f₁ - f₂|
Q.826Medium
A sound source moves towards a stationary observer with velocity v_s. The observer hears frequency f'. The actual frequency of the source is f. The relationship is:
Answer: B
For source moving towards stationary observer: f' = f × v/(v - v_s), so f = f'(v)/(v + v_s) when rearranged
Q.827Easy
A string of length 1 m is fixed at both ends. The fundamental frequency is 100 Hz. What is the frequency of the third harmonic?
Answer: C
For a string fixed at both ends, f_n = n × f₁. Third harmonic: f₃ = 3 × 100 = 300 Hz
Q.828Medium
A wave on a string has amplitude A = 5 cm and period T = 0.2 s. The maximum velocity of a particle on the string is:
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.830Medium
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.831Easy
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.832Medium
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.833Easy
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.834Medium
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:
