Cyberphysics - Waves Revision
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- What does a wave do?
- A wave transports energy from one place to another
- What are mechanical waves?
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Mechanical waves use particles to transfer energy (neighbouring particles bump into each other and set their neighbours moving).
Eg. sound waves use air particles so it cannot travel through a vacuum (a vacuum is empty space with no particles in it at all!). Sound travels faster through solids than liquids than gases because the particles are more closely packed. - What are electromagnetic waves?
- Electromagnetic waves don't use particle vibration to transfer their energy (in fact particles interrupt their progress through a material) and can therefore travel through a vacuum. e.g. light
- What is the unit of frequency?
- Frequency is measured in hertz (Hz)
- What is the wave equation?
- wavespeed = frequency x wavelength
- Define a longitudinal wave.
- The vibrations in a longitudinal wave are parallel to the direction in which the energy is travelling. Eg. sound.
- Define a transverse wave.
- The vibrations in a transverse wave are perpendicular (at right angles) to the direction in which the energy is travelling. Eg. light.
- Define wavelength.
- Wavelength (lamda a Greek letter 'l') is the shortest distance between two particles that are oscillating in phase. (Distance between two crests on a displacement/distance graph). It is measured in metres (m)
- What is the period of a wave?
- Period (T) is the time taken for one complete oscillation of a particle in the wave. (Distance between two crests on a displacement/time graph). It is measured in seconds (s).
- What is amplitude?
- Amplitude (A) is the maximum displacement from the mean position. (To the top of a crest or bottom of a trough from the middle line in either graph).
- What is frequency?
- Frequency (f) is the number of oscillations per second. It cannot be read directly off a graph. You need to find (T) from the displacement/time graph and then find its reciprocal (f =1/T)
- What are analogue signals?
- Analogue signals contain all the information as a continuously varying wave
- What are digital signals?
- Digital signals are a series of pulses - either high or low - on or off - sometimes expressed as binary code 1s and 0s.