# A longitudinal wave of frequency 1000 Hz is travelling in a medium . At a certain point in the medium there is a compression at certain moment . How many milliseconds later would the next rare faction form at this place ? If the velocity of wave is 350 m/s , how for is the earlier compression at this time ?

$(a)\;0.35\;m\qquad(b)\;0.7\;m\qquad(c)\;0.175 \;m\qquad(d)\;0.2 m$

Answer : (c) $\;0.175 \;m$
Explanation :
As time taken is half of the time period , earlier compression , is at a distance of $\;\large\frac{\lambda}{2}\;$ from rarefaction
But $\;\lambda=\large\frac{v}{\nu}=\large\frac{350}{1000}=0.35$
distance (d)$\;=\large\frac{0.35}{2}$$=0.175$
edited Mar 12, 2014 by yamini.v