3.2 understand the difference between longitudinal and transverse waves and describe experiments to show longitudinal and transverse waves in, for example, ropes, springs and water
Transverse waves oscillate perpendicular to the direction of travel, and look like this:
Longitudinal waves oscillate parallel to the direction of travel, and look like this:
Transverse waves are able to travel in a vacuum, longitudinal waves require particles to be able to transfer energy.
You can see transverse waves by holding a rope and jerking it up and down. It will form the 'S' shape that is recognisable as a transverse wave.
You can see longitudinal waves by stretching out a spring, then moving your hand backwards and forwards to create compressions in the spring.
You can use a wave tank to see longitudinal oscillations; a vibrating bar is placed at one end of the tank, creating waves as it moves. By shining a light through, the waves can be projected onto paper underneath, or onto the ceiling.
3.3 define amplitude, frequency, wavelength and period of a wave
Amplitude: How high a wave goes, how big it is. The distance from 0 to the crest of the wave.
Frequency: How many waves pass in a certain period of time
Wavelength: The distance between the same points of two consecutive waves (e.g. two crests or two troughs)
Period: How long it takes for one wavelength to travel past a certain point
3.4 understand that waves transfer energy and information without transferring matter
We know that waves are able to transfer energy and information without transferring matter because we can get the information through matter. Light is able to travel through solid glass, and we can hear people talking through walls and doors. These objects do not move, but we still receive the energy and information through waves.
3.5 know and use the relationship between the speed, frequency and wavelength of a wave:
wave speed = frequency × wavelength
v = f × λ
This relationship is important, as it helps us to calculate a variety of different quanities that are necessary in this topic.
3.6 use the relationship between frequency and time period:
frequency = 1 / time period
f = 1 / t
3.7 use the above relationships in different contexts including sound waves and electromagnetic waves
Using the triangle method, you can manipulate different questions to answer it correctly.
3.8 understand that waves can be diffracted when they pass an edge
When waves hit an edge, they can be diffracted to spread around the space as shown in the diagram below
3.9 understand that waves can be diffracted through gaps, and that the extent of diffraction depends on the wavelength and the physical dimension of the gap.
When a wave passes through a gap, it is forced through, and then once it is able to reach the other side it can spread out:
How much the wave is diffracted depends on the width of the gap, and the wavelength. The smaller the gap in proportion to the wavelength, the bigger the diffraction effect.
