Air movement causes ripples in water
This is what gives the ripples on a lake their transient, sparkling appearance, as they briefly rise and catch the light before settling back into stillness.
Even on a day when there is no wind, there will always be some movement in the air, and at the surface of a water body, that movement causes small ripples to form. Wind energy is being transferred to the minuscule water molecules, which begin to move up and down, gently rising and falling, pulling along with the molecules beside them.
However, the surface tension of water is quite strong, due to the polar nature of water molecules, and this tension will stop the ripples from perpetuating very far or for very long. The energy transferred into the water is quickly used up in moving those molecules up and down, so the ripples fade. This is what gives the ripples on a lake their transient, sparkling appearance, as they briefly rise and catch the light before settling back into stillness.
When you throw a rock into a body of water, the rock will push water out of its way as it enters, causing ripples to move away from its point of entry in a circle or ring shape. Water will then rush back in to fill the empty space, which can often cause a splash, resulting in more ripples forming. The larger the rock, the greater the effect and the stronger the ripple, meaning that it will last longer before disappearing.
The reason that these ripples don’t behave like waves on a beach is because they aren’t strong enough. They lack the energy to persist in the face of water’s strong surface tension.
These types of ripples may also form when water is moving in a certain direction and encounters an obstacle, such as a fishing boat, a breakwall, or even your feet.
Water molecules will encounter an object and move upwards against it, before being pulled back down by the neighbouring molecules. This interaction causes a ripple to form that moves in the opposite direction of the water’s initial motion.A ripple is a type of wave motion — a capillary wave, to be precise.
