One side of the wave changes speed before the other side, causing the wave to move
<span>Dark Energy causes the Universe to accelerate outward. Dark Matter is the stuff that keeps the Universe together. </span>
Speed of wave is given as

Wavelength of the wave is given as

now from the formula of wave time period we can say




so it will have time period of T = 4 s
<h2>Sorry, But I don't know!!</h2>
Answer:
v=wavelength ×f
wavelength=v/f=455/655=0.694m