Transverse: vibrations perpendicular to the direction of travel of the wave. Longitudinal: vibrations parallel to the direction of travel of the wave. Sound waves are longitudinal so they cannot be polarised.
Polarised: the wave vibrations occur in one plane only Unpolarised: the wave vibrations occur in all planes perpendicular to the direction of travel. Related questions What color light has the highest frequency? Question afab2. Question f8ff1. Question afab6. Question afaba.
Russell you can see energy move to the right while individual particles vibrate up and down about fixed points. Electromagnetic waves X-rays, light, radio, radar and TV waves are examples of transverse waves formed by electric and magnetic fields vibrating together at right angles to the wave's motion.
They don't need any medium so they can move through a vacuum, good for us or we wouldn't see the Sun! They all move at the same speed of , km.
They slow down when they travel through a medium this is an average speed between interactions. Mechanically twisting or pulling a medium sideways is called shearing so waves formed this way are also called shear waves. Longitudinal and Transverse waves together Sometimes longitudinal and transverse waves occur together.
Ocean waves are a combination of longitudinal and transverse waves because the surface of the water can be pulled sideways as well as pushed longitudinally. Russell you can see energy move to the right while individual particles move clockwise in circles or ellipses. When ocean waves get to a shelving beach the speed of the waves changes relative to each other and circles go to ellipses and then the wave breaks.
Seismic waves are formed when there is a sudden movement or slip between layers in the Earth's crust. This may happen anywhere between several km and several s km down from the surface. The wave motions that occur through the crust have Pressure "P" components and Shear "S" components. The P waves move at 5 - 14 km.
Note: seismic waves can also have "surface" waves. Again see Dr. Russell 's excellent pages for details. Measuring Waves Waves have peaks maxima and troughs minima. The maxima link to form "wavefronts" which can be lines like "lines of breakers" at the beach or more generally areas. Plane or "Straight" waves have wavefronts which are planes seen as straight lines in 2 dimensions.
The direction that a wave travels or "propagates" is always at right angles to the wavefronts and usually indicated by arrowed lines or "rays". It is half the measurement between a minimum to a maximum and can be a height or a pressure etc. It is usually given the symbol T, and measured in seconds. The unit of frequency is s -1 , which is given the special name Hertz.
When v velocity is hand written it is usually round at the bottom. Example 3. Find the frequency of the waves. Find the wavelength of these waves.
Find the wave speed. Phase difference The moon has phases, which go from new, to 1 st quarter, to full, to 3 rd quarter etc. The phase of something tells us how far through a cycle it is.
Radians are the preferred unit. To understand radians, think of a circle with two radii drawn from the centre outwards to the circular curve. In the diagram above the lines on the filters represent a 'grid' that the wave components can get through in the same way as the rope waves - they do NOT represent the orientation of the chains of molecules that absorb the waves. When you look at a piece of polaroid film you cannot see any lines on it at all!
If you align two polaroid filters and then steadily rotate one of them you will find that less leght gets through until when you have rotated the second filter 90 degrees no light gets through.
As you continue to rotate the filter the amound of light getting through the filter combination will increase until you get to the point when the total rotation of the filter is degrees. When in this position you will have the same amount getting through as you had in the first place. Whether a wave undergoes plane polarisation is therefore a test for a transverse wave. This can be done for visible light using two strips of polarisaing film or for microwaves using a 1 cm metal grid.
Two grids at right angles to each other will absorb all of the microwaves - hence microwave sources are surrounded by a fine mesh. In order for an aerial to receive plane polarised radiowaves it has to be lined up parallel to the electric component of the electromagnetic wave. It will then absorb the energy as it is used to make electrons in the aerial vibrate - like the 'bars' in the illustration above.
Remember an aerial wants to absorb the radiation - not allow it to pass through unimpeded. For Malus' Law see here.
Light reflecting off water or any other shiny but non-metallic surface will be partially polarised ; this is because the component of the light which is perpendicular to the surface is inverted by being reflected, and interferes with itself destructively. See polaroid sunglasses. Optically active and birefrigement substances. Optically active substances actually rotate the polarisation of light passing through them, while birefringent materials refract light by different amounts depending on its polarisation.
An example of this is the mineral calcite, which produces clear double images by splitting the incoming light into two streams with complementary polarisations. Polaroid sunglasses. Liquid Crystal Display s.
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