A train standing at the outer signal of a railway station blows a whistle of frequency $400\mathrm{Hz}$ in still air. The train begins to move with a speed of$10 \text{m/s}$  towards the platform. What is the frequency of the sound for an observer standing on the platform? (sound velocity in the air $=330 \mathrm{m}/\mathrm{s}$)

The wave pattern on a stretched string is shown in Figure. Interpret what kind of wave this is and find its wavelength.

The pattern of standing waves formed on a stretched string at two instants of time is shown in Figure. The velocity of two waves super-imposing to form stationary waves is $360 {\mathrm{ms}}^{-1}$ and their frequencies are $256 \mathrm{Hz}$.

(a) Calculate the time at which the second curve is plotted.

The pattern of standing waves formed on a stretched string at two instants of time are shown in Figure. The velocity of two waves super-imposing to form stationary waves is $360 {\mathrm{ms}}^{-1}$ and their frequencies are $256 \mathrm{Hz}$.

(b) Mark nodes and antinodes on the curve.

The pattern of standing waves formed on a stretched string at two instants of time are shown in Fig. The velocity of two waves superimposing to form stationary waves is $360 \text{m/s}$ and their frequency is $256 \text{Hz}$.

Calculate the distance between A' and C'.

A tuning fork vibrating with a frequency of $512 \mathrm{Hz}$ is kept close to the open end of
a tube filled with water (Figure). The water level in the tube is gradually lowered. When the water level is $17 \text{cm}$ below the open end, the maximum intensity of sound is heard. If the room temperature is $20°\mathrm{C}$, calculate

(a) speed of sound in air at room temperature