INTRODUCTION TO WAVES

WAVES Waves are a disturbance that travels through space or matter Waves transmit energy

TYPES OF WAVES There are 2 types of waves 1.Longitudinal Waves A longitudinal wave is when the displacement is in the same direction (parallel to) that the energy is travelling Example – Think of a Slinky. If you stretch out a slinky and push in one side, it will bunch up in one area. That bunched up area will travel forward through the slinky. This is an example of a longitudinal Wave These are sometimes called pressure waves or compression waves

TYPES OF WAVES Longitudinal Waves Longitudinal waves are mechanical waves Mechanical waves transmit energy through a medium, such as matter In a longitudinal wave, there are 2 main areas that we see Compression – where all of the particles are bunches together Rarefaction – where the particles are spread far apart Examples of longitudinal waves are sound waves or p- waves during an earthquake

TYPES OF WAVES Sound waves act as longitudinal waves Sound waves are created when force is exerted on air The air bunches together where it was pushed The air that was pushed runs into other air particles and transmits its energy This moves the wave forward, transmitting energy Compression Rarefaction

TYPES OF WAVES Earthquakes and longitudinal waves Earthquakes are felt after the tectonic plates of the Earth shift This transmits energy through the Earth itself We feel this as an earthquake The P-Wave is a longitudinal wave and is the first wave felt in an earthquake

TYPES OF WAVES 2.Transverse Waves A transverse wave is when the displacement is perpendicular to the direction the energy is travelling. Example – Think of a rope. If you move the end of the rope up and down, the rope will form a wave pattern and the energy will travel down the rope.

TYPES OF WAVES Transverse Waves Transverse waves can be mechanical waves This means then can travel through matter Transverse waves can also be electromagnetic waves These are waves that can travel through a vacuum or space They do not need matter to continue moving. We usually call electromagnetic waves light

TYPES OF WAVES Earthquakes also produce transverse waves The second wave to hit in an earthquake is the s-wave It is a transverse wave It moves the ground side-to-side shaking the earth back and forth

TYPES OF WAVES Although longitudinal and transverse waves may look different, mathematically they are still the same A longitudinal wave can be plotted as areas of high particle density vs. time to make a repeating pattern A transverse wave, when plotted, shows the same pattern over time

THE MATHEMATICS OF PERIODIC WAVES To understand how periodic waves work, we must be able to identify the parts of a periodic wave Crest – The peak, or top, of the wave Trough – the bottom of the wave

THE MATHEMATICS OF WAVES Amplitude – the height (or low) that a wave reaches from the resting point This is NOT the maximum movement of the wave up and down Essentially it is how high or how low a wave goes from the middle

THE MATHEMATICS OF WAVES Period – The period is the time that it takes for a wave to complete one cycle Basically how long it takes (in seconds) for a wave to go from peak-to-peak or trough-to-trough A wave’s period is measured in seconds/cycle (s/cycle) Period gets the symbol T.

THE MATHEMATICS OF WAVES Frequency – the frequency of a wave is the inverse of the period (1/T) It is the number of cycles that wave can complete in 1 second If you could only see one portion of a wave and watched it for one second, the number of times the string moved up, down, and up again would be the frequency. Frequency is measure in the units cyles/second Cycles/second is also called Hertz (Hz) Frequency gets the symbol f

THE MATHEMATICS OF WAVES Wavelength – the distance it takes for a wave to complete one cycle Basically, how far a wave travels to go from peak-to-peak or trough-to-trough Wavelength is a distance and is measured in metres/cycle We usually don’t worry about saying cycle because we know it is a wave and it is completing cycles Wavelength gets the symbol lambda (λ)

THINGS YOU SHOULD KNOW Wave Longitudinal Wave Mechanical Wave Transverse Wave Electromagnetic Waves Crests Troughs Amplitude Period Frequency Wavelength