# Get the Knowledge that sets you free...Science and Math for K8 to K12 students

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## Waves and Optics

Ocean waves Ocean waves are an example of circular superposition of longitudinal and transverse waves.
Artificial Guide Star A beam of Laser is projected up at about 100km hits the sodium atoms of the atmosphere. It excites them to emit yellow light in all directions, creating a glowing Guide Star in the upper atmosphere. This is used by astronomers to carry measurement. The center of the Milkyway can be observed with the Laser Guide Star.
Standing waves in guitar In general, the standing waves form only if the length of a vibrating cord of the guitar is a multiple of one-half wavelength. Certain points on the wave that are stationary are called nodes. Points where a crest or trough occurs midway between two nodes are called antinodes.

A wave is an oscillation that travels through space in time, accompanied by the transfer of energy. Waves travel and the wave motion transfers energy from one point to another. It is generally not accompanied by a motion of the medium occupying the space as a whole. Transverse waves occur when a disturbance creates oscillations perpendicular to the propagation i.e the direction of energy transfer. Longitudinal waves occur when the oscillations are parallel to the direction of propagation. Waves are described by a wave equation which sets out how the disturbance proceeds over time.

Waves of transverse displacement, traveling along a stretched string are mechanical waves, which propagate through a medium in which the substance of this medium is deformed. The deformation reverses itself owing to restoring forces resulting from its deformation. It is a 'standing wave' in which energy is moving in both directions equally. Electromagnetic waves including visible light, ultraviolet radiation, infrared radiation, gamma rays, X-rays and radio waves can travel through empty space.

Electromagnetic wave consists of periodic oscillations in electrical and magnetic fields. The inherent interaction of its components is the main reason of its motion and broadcasting. Properties of waves include reflection, refraction, interference, dispersion and diffraction.

Light, the source of ‘life’ is energy that creates and sustains life in all its varied colors and forms. Light or visible light is electromagnetic radiation that is visible to the human eye, and is responsible for the sense of sight. Primary properties of light are intensity, propagation direction, frequency and polarization. The speed of light in a vacuum is about 299,792,458 meters per second. Albert Einstein invented Photo–electric effect that won him the Nobel prize. Light which is emitted and absorbed in tiny “packets” called photons, exhibits properties of both waves and particles. This property is referred to as the wave–particle duality. His equation combining energy with the speed of light is perhaps one of the most famous equation in physics. Light has an equally important sway in contemporary technologies like fiber optics and LASERs.

Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. During propagation, waves can be reflected, refracted, or attenuated by the medium. Sound waves are also described in terms of sinusoidal plane waves, which are characterized by the generic properties - frequency, wavelength, wave number, intensity and speed.

Sound is transmitted through gases, plasma, and liquids as longitudinal waves, also called compression waves. Sound can be transmitted as both longitudinal waves and transverse waves through solids.

Longitudinal sound waves are waves of alternating pressure deviations from the equilibrium pressure, causing local regions of compression and rarefaction, while transverse waves in solids are waves of alternating shear stress at right angle to the direction of propagation.