$\lambda=\frac{v}{\nu}$
$\lambda=\frac{340}{340}=1 m$
Therefore for different resonances, the required lengths of the air column are
$\frac{\lambda}{4}, \frac{3 \lambda}{4}, \frac{5 \lambda}{4}$ i.e. $25 \mathrm{cm}, 75 \mathrm{cm}, 125 \mathrm{cm}$
As the length of pipe is120cm, the resonance corresponding to $125 \mathrm{cm}$ is not possible.
So, when the water is slowly poured, the first resonance will occur at length
$75 \mathrm{cm}$ of air column. Hence, the height of water is
$h=120-75=45 \mathrm{cm}$

$(a)$ Every particle has a fixed amplitude which is different from the amplitude of its nearest particle.
$(b)$ All the particles cross their mean position at the same time.
$(c)$ All the particles are oscillating with same amplitude.
$(d)$ There is no net transfer of energy across any plane.
$(e)$ There are some particles which are always at rest.
Which of the following is correct
$(i)\,\,\,\,\,{y_1} = A\,\cos \,\,2\pi \,\left( {{n_1}t\, + \,\frac{x}{{{\lambda _1}}}} \right)$
$(ii)\,\,\,\,\,{y_2} = A\,\cos \,\,2\pi \,\left( {{n_1}t\, + \,\frac{x}{{{\lambda _1}}} + \pi } \right)$
$(iii)\,\,\,\,\,{y_3} = A\,\cos \,\,2\pi \,\left( {{n_2}t\, + \,\frac{x}{{{\lambda _2}}}} \right)$
$(iv)\,\,\,\,\,{y_4} = A\,\cos \,\,2\pi \,\left( {{n_2}t\, - \,\frac{x}{{{\lambda _2}}}} \right)$
The pairs of waves which will produce destructive interference and stationary waves respectively in a medium, are