The frequency of the first overtone of a closed pipe of length lc is equal to that of the third overtone of an open pipe of length lo. the ratio `(l_o)/(l_c)` is equal to
`(4)/(5)`
`(3)/(8)`
`(7)/(6)`
`(8)/(3)` .
i didn't understand the frequency of first overtone close pipe and open pipe