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Least Distance Between Two Successive Crests in Wave

A transverse wave on a string is described by y=3sin(36t+0.018x+π/4)y = 3\sin (36t + 0.018x + \pi/4), where x,yx, y are in cm\text{cm} and tt in seconds. The least distance between the two successive crests in the wave is  cm\underline{\quad\quad}\text{ cm}. (Nearest integer)

(π=3.14)(\pi = 3.14)

Official Numerical Answer349

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Step-by-Step Solution

A transverse wave on a string is described by the equation: y=3sin(36t+0.018x+π4)y = 3\sin\left(36t + 0.018x + \frac{\pi}{4}\right)

Comparing this with the standard wave equation y=Asin(ωt+kx+ϕ)y = A\sin(\omega t + kx + \phi), we get the wave number kk as: k=0.018 cm1k = 0.018 \text{ cm}^{-1}

The least distance between two successive crests of a wave represents its wavelength (λ\lambda). The relation between the wavelength λ\lambda and the wave number kk is given by: k=2πλk = \frac{2\pi}{\lambda}

Rearranging for λ\lambda: λ=2πk\lambda = \frac{2\pi}{k}

Given π=3.14\pi = 3.14, substituting the values into the formula gives: λ=2×3.140.018=6.280.018=628018=31409348.89 cm\lambda = \frac{2 \times 3.14}{0.018} = \frac{6.28}{0.018} = \frac{6280}{18} = \frac{3140}{9} \approx 348.89 \text{ cm}

Rounding off to the nearest integer, we get: λ349 cm\lambda \approx 349 \text{ cm}

Least Distance Between Two Successive Crests in Wave | Physics PYQ Solution - JEE Challenger