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# Wavelength of a wave in a certain medium is 20 cm and its velocity is 350 m/s . The same wave is transmitted into a medium where the velocity is 1400 m/s . Its wavelength in the medium would be ?

$(a)\;20\;cms\qquad(b)\;60\;cms\qquad(c)\;50\;cms\qquad(d)\;80\;cms$

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A)
Answer : (d) $\;80\;cms$
Explanation :
As the same wave is transmitted from one medium to another , frequency of the wave remains same .
frequency = $\;\large\frac{v_{1}}{\lambda_{1}}=\large\frac{v_{2}}{\lambda_{2}} \quad => \large\frac{350}{20} =\large\frac{1400}{\lambda_{2}}$
$\lambda_{2}=80\;cms\;.$