3.3 Transverse and Longitudinal Waves Flashcards
What is a transverse wave?
A wave where the displacement of the particles (vibrations) is at right angles to the direction of energy propagation/transfer
What are examples of transverse waves?
- EM waves
- ripples on water
- waves on strings
- some types of earthquake shock waves (S-waves)
What are the two ways transverse waves can be drawn?
- as graphs of displacement against distance
- as graphs of displacement against time
What is a longitudinal wave?
A wave where the displacement of the particles (the vibration) is along the direction of energy propagation/transfer
What are examples of longitudinal waves?
- sound waves
- some types of earthquake shock waves (P-waves)
What do longitudinal waves consist of?
Alternate compressions and rarefactions of the medium its travelling through
How are longitudinal waves represented graphically?
They are usually seen plotted as displacement against time
What is a polarised wave?
A wave that oscillates in one direction only
What can a polarising filter be used for?
Ordinary light waves are a mixture of different directions of vibration
A polarising filter can be used to polarise light and other waves
It only transmits vibrations in one direction
What happens if you have two polarising filters at right angles to each other?
No light will get through
What happens if you have two polarising filters at non-right angles to each other?
The second filter only blocks out all of the light when the transmission axis is at right angles to the plane of polarisation
Otherwise, it just reduces the intensity of the light passing through it
How does polarisation provide evidence for the nature of transverse waves?
Polarisation can only happen for transverse waves
Why can light be polarised?
Light is a transverse wave consisting of vibrating electric and magnetic fields perpendicular to the direction of energy transfer
How is polarisation used in glare reduction?
- most light you see is unpolarised
- light reflected off some surfaces is partially polarised (the amount of polarisation depends on the angle of the incident light)
- when light is reflected by surfaces such as water, glass or tarmac enters the eye it can cause glare
- you can block out some of the reflected polarised light with a polarising filter
- this reduces the intensity of the light entering your eye
How is polarisation used in improving TV and radio signals?
- TV and radio signals are polarised by the orientation of the rods on the transmitting aerial
- to receive a strong signal, you have to line up the rods on the receiving aerial to the rods on the transmitting aerial
