In physics

Physics

Physics is a natural science that involves the study of matter and its motion through spacetime, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.Physics is one of the oldest academic...

 and engineering

Engineering

Engineering is the discipline, art, skill and profession of acquiring and applying scientific, mathematical, economic, social, and practical knowledge, in order to design and build structures, machines, devices, systems, materials and processes that safely realize improvements to the lives of...

, a ripple tank is a shallow glass tank of water used in schools and colleges to demonstrate the basic properties of wave

Wave

In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...

s. It is a specialized form of a wave tank

Wave tank

A wave tank is a laboratory setup for observing the behavior of surface waves. The typical wave tank is a deep and narrow, transparent-sided box filled with liquid, usually water, leaving open or air-filled space on top. At one end of the tank an actuator generates waves; the other end usually...

. The ripple

Capillary wave

A capillary wave is a wave traveling along the phase boundary of a fluid, whose dynamics are dominated by the effects of surface tension.Capillary waves are common in nature and the home, and are often referred to as ripples...

 tank is usually illuminated from above, so that the light shines through the water. Some small ripple tanks fit onto the top of an overhead projector

Overhead projector

An overhead projector is a variant of slide projector that is used to display images to an audience.-Mechanism:An overhead projector typically consists of a large box containing a very bright lamp and a fan to cool it. On top of the box is a large fresnel lens that collimates the light...

, i.e. they are illuminated from below. The ripples on the water show up as shadow

Shadow

A shadow is an area where direct light from a light source cannot reach due to obstruction by an object. It occupies all of the space behind an opaque object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, or reverse projection of the object blocking the...

s on the screen underneath the tank.