When a wave propagating in one medium enters another medium,which of the following characteristics remains constant?

$A$ sinusoidal wave of frequency $500 \,Hz$ has a speed of $350 \,m/s$. The phase difference between two displacements at two points separated by a distance of $1 \,m$ is ...........

The diagram below shows the propagation of a wave. Which points are in the same phase?

The path difference between two waves given by the equations $y_1 = a_1 \sin \left(\omega t - \frac{2 \pi x}{\lambda}\right)$ and $y_2 = a_2 \sin \left(\omega t - \frac{2 \pi x}{\lambda} + \phi\right)$ is

In a simple harmonic wave,the minimum distance between particles in the same phase always having the same speed is ..........

In a sinusoidal wave,the time required for a particular point to move from maximum displacement to zero displacement is $0.170\,s$. The frequency of the wave is .... $Hz$.