• question_answer A string is clamped at both the ends and it is vibrating in its 4th harmonic. The equation of the stationary wave is $Y=0.3\sin$$(0.157x)cos$$(200\pi t)$. The length of the string is : (All quantities are in SI units.)             [JEE Main 9-4-2019 Morning] A) 20 m               B) 80 mC) 60 m               D) 40 m

4th harmonic $4\frac{\lambda }{2}=\ell$                                      $2\lambda =\ell$ From equation$\frac{2\pi }{\lambda }=0.157$ $\lambda =40$ $\ell =2\lambda$ $=80m$ Option [b]