Dear Student,

well according to the question, it is given that the velocity of sound at room temperature is 350m/s

Air column length is 70 cm

1- Closed at one end- Means it will act as a closed organ pipe system

As we know the fundamental frequency is equals to (N)= V/4l

hence calculating N as we have l= 0.7m and V= 350m/s, we get N= 125 Hz

as it is closed from one end we have to take odd fundamental frequencies

------->Pth overtone= (2p+1)*n, since we have to calculate for 2nd overtone p=2

we get, frequency for 2nd overtone = 625Hz

Similarly you can get frequency for open at both ends as we have to take even number of fundamental frequency.

Hope this will able to help your sound waves concept