The different colors of visible light waves comprise a tiny portion of the overall electromagnetic spectrum.
There are two distinct kinds of waves: mechanical and electromagnetic. Mechanical waves transmit energy through a medium by the mechanical interaction between physical particles. There are three types of mechanical waves: transverse, longitudinal and complex mechanical waves. Electromagnetic waves, which can flow through a vacuum, do not transmit energy by mechanical means, but by electrical currents and magnetic fields.
Transverse Waves
Transverse waves, also known as shear waves, transmit energy through a medium by displacing particles in a direction that is perpendicular to the direction of propagation. This is similar to vibrating one end of a taut rope. Segments of the rope are displaced vertically, while the energy is propagated down the length of rope. Seismic waves known as S waves, or secondary waves, are an example of a transverse wave. Love waves are another form of transverse seismic waves. Particles in an S wave are displaced vertically, while those in a Love wave are displaced horizontally. Transverse waves are shear waves and can only propagate through solids.
Longitudinal Waves
Longitudinal waves, also known as pressure waves, transmit energy through a medium by displacing particles in a direction that is parallel to the direction of propagation. This is similar to the motion of a Slinky. Longitudinal waves represent a change in the volume of the medium, created by the compression and rarefaction of the medium. As the energy passes through the medium, particles are pushed forward, compressing the medium, then pushed backwards. Seismic waves known as P waves, or primary waves, and sound waves are examples of longitudinal waves. These waves can travel through solids, liquids and gases.
Complex Mechanical Waves
Complex mechanical waves transmit energy through a medium by displacing particles in a direction that is both parallel and perpendicular to the direction of propagation. The overall displacement of the particles follows an elliptical motion, combining both a tranverse and longitudinal wave pattern. Water waves and seismic Rayleigh waves are examples of complex mechanical waves. The particles in a water wave move in a clockwise elliptical pattern, while particles in a Rayleigh wave move in a counter clockwise elliptical pattern.
Electromagnetic Waves
Electromagnetic waves transmit energy by means of electrical and magnetic fields that oscillate perpendicular to each other, and to the direction of propagation, and travel at the speed of light. What makes these waves different from mechanical waves is that they do not depend on the interaction between physical particles, and can therefore propagate through vacuums. The electromagnetic spectrum ranges from waves with the longest wavelengths, radio waves, to the smallest wavelengths, Gamma waves. These waves can also be described in terms of their energy and frequency. As wavelength decreases, both energy and frequency increase. This explains why X-rays and Gamma rays can penetrate so deeply into materials (small wavelength) and do so much damage at the cellular level (high energy).
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