What do the crests and troughs of light waves indicate?

If we represent light wave by E=EoSin(wt-kx) in one dimension then the points of maximum E that is Eo in the upward direction are called crests and points of maximum E(=Eo) in downward direction are called troughs. In the wave eq. read more

Like all waves, light waves have crests, their highest points, and troughs, their lowest points. In places where the crests coming from one slit extend over the crests coming from the other slit, the result is an intensification of light, and light bands appear on the detecting screen. read more

Sound waves themselves don’t really have crests and troughs like ocean waves. When the air pressure variation is graphed however generally the positive y direction is higher pressure and the negative y direction is lower air pressure. The zero point on the y axis would be “normal” air pressure, i.e., no sound wave present. read more