# Waves

## Moving Mass vs. Waves

Energy can be transferred by two methods- moving mass or waves. When energy is carried by moving mass, it takes the form of the kinetic energy of the moving matter. Energy is transferred when mass moves from the source of energy to the place where the energy is delivered. When waves carry energy, there are organized vibrations that move from the source of energy to the place where energy is delivered, but no matter travels along with the waves. Waves can be categorized in two types- mechanical or electromagnetic waves.

A stadium wave is a good example of a wave. While the people participating in the wave stand up and sit down to simulate the disturbance caused by energy traveling, the participants do not move to the left or right out of their seat and therefore no mass is traveling with the wave.

World record for Biggest Wave Ever !! Bristol Tenn. 130k +

## Mechanical Waves

Mechanical waves transfer mechanical energy through highly organized vibrations of particles. Mechanical waves must travel through matter. If there are no particles to vibrate, mechanical waves cannot exist. When mechanical waves pass through a substance they can move in two different ways. One type of wave causes the particles to oscillate back and forth along the direction of motion of the wave. This type of wave, where the vibration is parallel to the direction in which the wave moves is called a longitudinal wave. Another type of wave will cause the particles to vibrate back and forth along a direction that is perpendicular to the direction of motion of the wave. This type of wave is called a transverse wave.

An example of longitudinal mechanical waves are sound waves. When the frequency of a sound wave is between 20Hz and 20,000Hz the energy carried by the sound waves activated the human sense of hearing. The video below shows the disturbance in different liquid caused by sound waves.

Liquid Audio: Sound Wave Experimentation

## Electromagnetic Waves

Electromagnetic waves are disturbances in the electric fields and magnetic fields that are created by moving charged particles and carry electrical energy and magnetic energy. This energy is transported without the need for vibrating particles, so electromagnetic waves can be transported through the vacuum of space. Electromagnetic waves are divided into seven groups of waves, depending on the amount of energy, amplitude, and frequency of the wave. This is called the Electromagnetic Spectrum.

An example of an electromagnetic wave is visible light. The video below shows how electromagnetic waves are used in our daily lives.