When a stationary wave is formed,what is its frequency?

In stationary waves,the distance between a node and its nearest antinode is $20 \ cm$. The phase difference between two particles having a separation of $60 \ cm$ will be

What kind of waves can survive as standing waves?

The given diagram shows a detector placed between a transmitter of sound waves and a metal plate. At three adjacent points,$R, S$ and $T$,the meter shows zero intensity. Which of the following is the frequency of the emitted wave in $Hz$? (Take the velocity of sound as $v = 300 \, m/s$)

Two travelling waves of equal amplitudes and equal frequencies move in opposite directions along a string. They interfere to produce a stationary wave whose equation is given by $y = (10 \cos \pi x \sin \frac{2 \pi t}{T}) \, cm$. The amplitude of the particle at $x = \frac{4}{3} \, cm$ will be ........ $cm$.

What will be the change in phase of a wave due to reflection from a rigid support?