Properties of Waves Flashcards
What are the two types of waves?
- Transverse
- Longitudinal
What is a transverse wave?
A wave which oscillates at a right angle to the direction of energy transfer (direction of travel)
These can travel through a vacuum
What is a longitudinal wave?
A wave which oscillates parallel to the direction of energy transfer (direction of travel)
These cannot travel through a vacuum. Sound for example, are vibrations of air molecule, so need molecules to be able to travel
What are the key features of a transverse wave?
- Crest/peak (Highest point above midline)
- Trough (Lowest point below midline)
What are the key features of longitudinal waves?
- Compressions (Where the points are close together)
- Rarefactions (Where the points are far apart)
The wave will alternate between compressions and rarefactions - think of a slinky
What do waves transfer and what do they not transfer?
- They transfer energy and information
- They do not transfer matter
What is the definition of amplitude?
The distance from the midline of the wave to the crest/peak or the trough
What is the definition of wavelength?
- The distance from one wave to the same point on the next wave
- On transverse waves, it is the distance from one peak to the next
- On longitudinal waves, it is the distance from one compression to the next
What is the definition of frequency?
The number of waves passing a point per second
What is the time period of a wave?
The time taken for a single wave to pass a point
What are wavefronts?
- Ways of visualising waves by drawing them as vertical lines as seen from above
- If the lines are close together, the wavelength is small
- If the lines are far apart, the wavelength is large
What is the relationship between wave speed (velocity), frequency and wavelength?
- Wave Speed (velocity) = Frequency x Wavelength
- v = f x λ
What is the relationship between frequency and time period?
Frequency = 1/Time Period
F = 1/T
These equations can be applied to all types of waves
What is the doppler effect?
- The apparent change in wavelength and frequency of a wave emitted by a moving source (as the source moves)
- If the wavelength appears to decrease, the frequency appears to increase and vice versa
Why does the doppler effect occur?
- In front of the source when it is moving, the wavelengths appear squashed so are lower (and the frequency is higher), and behind the source they appear stretched out so the wavelength is higher (and the frequency is lower)
- An example is when a police car is driving towards you the pitch is high, but driving away the pitch is low
