Topic 6 - Waves Flashcards
What happens when waves travel through a medium?
The particles oscillate and transfer energy between each other. Overall the particles stay in the same place and only energy is tranferred.
What is the amplitude of a wave?
The maximum displacement of a point on the wave from its undisturbed position.
What is wavelength?
The distance between the same point on two adjacent waves (eg. between each trough).
What is frequency?
Number of complete waves passing a certain point per second, measure in hertz (Hz).
1 Hz =…
One wave per second.
What is the period of a wave?
The amount of time it takes for a full cycle of the wave.
How do you calculate the period?
Period (s) = 1/frequence (Hz)
What are the two types of wave?
Transverse or longitudinal.
What is a transverse wave?
One which the oscillations (vibrations) are perpendicular to the direction of energy transfer.
What are examples of transverse waves?
Electromagnetic waves (eg. light), ripples and waves in water and waves on a string.
What are longitudinal waves?
Oscillations are parallel to the direction of energy transfer.
What are examples of longitudinal waves?
Sound waves in air, ultasound, shock waves eg. some seismic waves.
What is wave speed?
The speed at which energy is being transferred or the speed at which the wave is moving at.
How can you calculate wave speed?
Wave speed (m/s) = frequency (Hz) x wavelength (m) v=fλ.
Descrribe how you can measure the speed of sound?
Attach a signal generator to speaker generating sounds with a specific frequency. Two microphones and an oscilliscope can find the wave length of the sound waves generated.
1) Set up the oscilliscope so the detected waves at each microphone are shown as seperate waves.
2) Start with both microphones next to the speaker, then slowly move away until the two waves are aligned on the display, but have moved one wavelength apart.
3) Measure the distance between the microphones to find one wavelength.
4) Use v=fλ to find speed. The frequency is whatever you set the signal generator to.
What is the rough speed of sound in air?
330 m/s.
How can you measure the speed of water ripples?
1) using a signal generator attached to the dipper of a ripple tank creates water waves at a set frequency.
2) use a lamp to see wave crests on a screen below the tank. make sure the size of the waves shadows are the same size of the waves.
3) the distance between each shadow is equal to one wavelength.
measure the distance between shadow lines that are 10 wavelengths apart, then divide distance by 10 to find the average wavelength. - good for measuring small wavelengths.
4) you can take a photo and measure shadows with a ruler.
5) use v=fλ to calculate the speed.
Why is this set up suitable for investigating waves (water)?
Allows you to measure the wavelength without disturbing the waves.
What do you need to make sure to do when measuring the spped of water ripples using a lamp?
Make sure you dim the lights.
How can you use the wave equation for waves on strings?
1) Set up experiment, turn on the signal generator and vibration transducer. the strings will start to vibrate.
2) Adjust the frequency of the signal generator until there’s a clear wave on the string.
3) Measure the wavelengths of the waves.
4) the frequence is whatever the signal generator is set to.
5) v=fλ
Wave equation for waves on strings: What does the frequency you need depend on?
Length of string between pully and transducer, masses you’ve used.
Wave equation for waves on strings: Why is the set up suitable for measuring waves on a string?
Easy to see and measure the wavelength.
What can happen when waves arrive at a boundary between two different materials?
They are absorbed, transmitted or reflected.
What happens when waves are absorbed?
It transfers energy to the materials energy stores.