JEE Main 2021 · PhysicsMultiple choiceSingle correctEasyConceptual

JEE Main 24 February 2021, Shift 2, Physics Q9

Question 9 of 90 in this shift, Physics question 9 of 30, Section A.

Which of the following equations represents a travelling wave ?

(1) $y = Ae^{x}\cos(\omega t - \theta)$
(2) $y = Ae^{-x^2}(vt + \theta)$
(3) $y = A\sin(15x - 2t)$ Official answer
(4) $y = A\sin x\ \cos\omega t$

Official answer

Option 3

NTA final key.

Chapter: Waves
Topic: Waves on Strings
Idea tested: Linear Wave Differential Equation

Same topic in other shifts

All Waves on Strings questions

2 Apr 2026, Shift 1 · Q35The equation of a plane progressive wave is given by $y=5\cos\pi\left(200\,t-\frac{x}{150}\right)$ where $x$ and $y$ are in cm and $t$ is…EasySingle correct
7 Apr 2025, Shift 2 · Q35The equation of a wave travelling on a string is $y=\sin[20\pi x+10\pi t]$ , where $x$ and t are distance and time in SI units. The minimum…MediumSingle correct
8 Apr 2025, Shift 2 · Q34Two strings with circular cross section and made of same material, are stretched to have same amount of tension. A transverse wave is then…EasySingle correct
8 Apr 2025, Shift 2 · Q40The amplitude and phase of a wave that is formed by the superposition of two harmonic travelling waves, $y_1(x, t) = 4\sin(kx - \omega t)$ …MediumSingle correct
5 Apr 2024, Shift 2 · Q55A sonometer wire of resonating length 90 cm has a fundamental frequency of 400 Hz when kept under some tension. The resonating length of…EasyNumerical value
1 Feb 2024, Shift 1 · Q54A tuning fork resonates with a sonometer wire of length 1 m stretched with a tension of 6 N. When the tension in the wire is changed to 54…MediumNumerical value

Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.