Two open organ pipes of fundamental frequencies $$n_1$$ and $$n_2$$ are joined in series. The fundamental frequecny of the new pipe so obtained will be :

A

$$(n_1+ n_2)$$

B

$$\frac{n_1 + n_2}{2}$$

C

$$\sqrt{n_1^2 + n_2^2}$$

D

$$\frac{n_1 n_2}{n_1 + n_2}$$