lanjut : Waves

See wave frequency at the Wave Parts Frequency Page.



Check out Parts of Waves online.



Explore the example of the transverse wave.



Longitudinal Waves



Longitudinal waves do not have crests and troughs because they do not move up and down but back and forth. Longitudinal waves travel through solid,liquid, and gas mediums. A crowded area of a wave is called a compression. A stretched-out area of a wave is called a rarefaction. A wavelength is the distance between successive compressions or rarefactions. The amplitude is the difference in pressure between the maximum compression and the resting state. Examples are sound waves, slinky waves and some earthquake waves.



Explore the example of the longitudinal wave.



Electromagnetic Waves



Electromagnetic waves are modeled after transverse waves. No medium is needed for electromagnetic waves. Electromagnetic waves are oscillating electric and magnetic fields. Wavelength is the distance between the crests or troughs. Amplitude is the difference between maximum field strength and zero. Examples are light waves, radio wave, and x-rays. Light waves come in a wide range of frequencies and wavelengths. The full range of light at different frequencies and wavelengths is called the electromagnetic spectrum.



Explore the wavelength of the electromagnetic spectrum.



Wave Speed



Wave speed equals the frequency times the wavelength.



wave speed = frequency x wavelength



wave speed = #Hz x m



The speed of a wave depends on the medium. Sound travels through air very well therefore we hear many things, but sound travels 3 to 4 times faster in water. Sound travels even faster through a solid, 15 to 20 times faster than through air. Kinetic theory explains differences in wave speed. The arrangement of particles in the medium determines how well waves travel through it. Light has an finite speed. Electromagnetic waves travel through empty space at a constant speed, the speed of light which is 300,000,000 m/s. The speed of light slows as it passes through any medium, especially through a solid or liquid.

The Doppler Effect



Pitch is determined by the frequency of sound waves. Pitch is how high or low it is. The frequency changes when the source of the wave is moving. For example, when an ambulance is standing still the sound waves spread out in equal circles in every direction. When the ambulance is moving, the sound wave produced are pushed closer together as the siren approaches and are spread further apart as it moves away. The change in the observed frequency of a wave resulting from the motion of the source or the observer is called the Doppler effect.



doppler effect







Wave Interactions



Reflection is simply the bouncing back of a wave when it meets a surface or boundary. Waves reflect at a free boundary reflect equal to the original wave. At a fixed boundary, the waves reflect and are turned upside down.



wave reflection



Look at the interactive wave reflection.



Diffraction is the bending of waves around an edge as it passes the edge. Waves can also bend by refraction.



diffraction



Refraction is the bending of waves when they pass from one medium into another.



refraction