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

$A$ standing wave having $3$ nodes and $2$ antinodes is formed between two atoms having a distance of $1.21 \; \mathring{A}$ between them. The wavelength of the standing wave is .... $\mathring{A}$

The equation of a stationary wave is given by $y = 0.8 \cos \left( \frac{\pi x}{20} \right) \sin (200 \pi t) \text{ cm}$. What is the distance between two consecutive nodes in cm?

Stationary waves of frequency $300\, Hz$ are formed in a medium in which the velocity of sound is $1200\, m/s$. The distance between a node and the neighbouring antinode is ... $m$.

$A$ string fixed at one end and free at the other is vibrating in its second overtone. The length of the string is $10 \ cm$ and the maximum amplitude of vibration of particles of the string is $2 \ mm$. Then the amplitude of the particle at $9 \ cm$ from the fixed end is

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