Wave Motion 5 Question 20
20. The displacement of particles in a string stretched in the $x$-direction is represented by $y$. Among the following expressions for $y$, those describing wave motion is (are)
(a) $\cos k x \sin \omega t$
(b) $k^{2} x^{2}-\omega^{2} t^{2}$
(c) $\cos ^{2}(k x+\omega t)$
(d) $\cos \left(k^{2} x^{2}-\omega^{2} t^{2}\right)$
$(1987,2 M)$
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Solution:
- (a) and (c) options satisfy the condition;
$$ \frac{\partial^{2} y}{\partial x^{2}}=(\text { constant }) \frac{\partial^{2} y}{\partial t^{2}} $$
