The displacement of a progressive wave is represented by $y = A\,sin \,(\omega t - kx)$ where $x$ is distance and t is time. Write the dimensional formula of  $(i)$ $\omega $ and $(ii)$ $k$.

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Now, $[\mathrm{LHS}]=[\mathrm{RHS}]$

$[y]=[\mathrm{A}]=\mathrm{L}$

because $\omega t-k x$ is dimensionless,

$[k x]=\mathrm{M}^{0} \mathrm{~L}^{0} \mathrm{~T}^{0}\therefore[\omega t]=\mathrm{M}^{0} \mathrm{~L}^{0} \mathrm{~T}^{0}$

$\therefore [k] \mathrm{L}=\mathrm{M}^{0} \mathrm{~L}^{0} \mathrm{~T}^{0}$

$\therefore[\omega] \mathrm{T}=\mathrm{M}^{0} \mathrm{~L}^{0} \mathrm{~T}^{0}$

$\therefore [k]=\mathrm{L}^{-1}\therefore[\omega]=\mathrm{T}^{-1}$

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