Wave properties up to level 6 Flashcards
Explain what a wave is
A wave transfers energy without transferring matter. This is done through passing on oscillations from one part of the medium to another.
What is the difference between a transverse wave and a longitudinal wave?
A transverse wave has oscillations (vibrations) which are perpendicular to the direction the wave is moving in
A longitudinal wave has oscillations which are parallel to the direction that the wave is moving in
Give an example of
a) an electromagnetic wave
b) a mechanical wave
a) Visible light
b) waves on a slinkey spring
Explain why electromagnetic wave can travel through a vacuum but mechanical waves (such as sound) cannot
Electromagnetic waves do not need a medium to travel through, this means that they can travel through a vacuum even through there is no particles in there
Mechanical waves require a medium to travel through. For sound waves the medium is vibrating air particles. As there are no particles in a vacuum there is nothing to pass on the sound waves. This means that the sound cannot pass through it.
Explain why wave speed depends on
- the wavelength of the wave
- the frequency of the wave
- The wavelength of the wave is the distance that the wave travels with each complete wave. If the wavelength is higher then the wave will travel further for each complete wave, meaning that it will be going faster
- The frequency of a wave is the number of complete waves that occur in one second. if there are more waves in a second, and each one travels a set distance, then it will travel further in that second. This results in it going faster.
State the wave speed equation
Example: what is the frequency of a wave that travels with a speed of 20m/s and has a wavelength of 4m?
Wave speed = frequency x wavelength
Wave speed is measured in meters per second (m/s)
Wavelength is measured in meters (m)
frequency is measured in Hertz (Hz)
Example:
frequency = wave speed/wavelength
= 20/4
= 5 Hz
What is the preiod of a wave?
What is the frequency of a wave?
What is the equation that links the two?
The period of a wave is the time it takes for one complete wave to pass a point. It is also the time for one complete oscillation (vibration) of any particle in the wave
The frequency of a wave is the number of complete wave that pass a point in one second. It is also the number of complete oscillations of the wave that occur in one second.
The equation that links them is:
frequency = 1/period
frequency is measured in Hertz (Hz)
period is meausred in second (s)
What is the amplitude of a wave?
The amplitude of a wave is the maximum height of the wave when measured from the equilibrium position.
What is the wavelength of a wave?
The wavelength of a wave is the distance from one place in a wave to the next identical point of the wave, for example peak to peak or trough to trough
What is the equilibrium position of a wave?
The equilibrium position is the position that the particles of the medium would be in if there were no wave present.
What is the peak of a wave?
What is the trough of a wave?
The peak of the wave is the highest point of the wave
The trough of the wave is the lowest point on the wave
Explain how to measure the speed of a water wave
- Set up the equipment as shown in the diagram
- turn on the ripple tank and set the frequency of the wave generator to a known frequency
- Take a picture of the waves, then measure the wavelength of the wave using the correct scale. This is done by measuring from one peak to the next
- use the equation:
Wave speed = frequency x wavelength
to find the speed of the wave
What is refraction?
Refraction is the bending of waves when they pass from one medium to another.
Which part of the diagram relate to each of these parts of refraction
a) Incident ray
b) emergent ray
c) Refracted ray
d) Angle of incidence
e) Angle of refraction
f) The normal
a) Incident ray = 5
b) emergent ray = 4
c) Refracted ray = 3
d) Angle of incidence = 6
e) Angle of refraction = 2
f) The normal = 1
Explain why refraction occurs
When the wave moves from one medium to the other the wavelength of the wave changes. As the wave hits the boundary at an angle, one side of the wave changes wavelength (and therefore speed) before the other. This causes it to change direction
When the wave moves into a more optically dense medium the wavelength shortens and it bends towards the normal
When the wave moves into a less optically dense medium the wavelength lengthens and it bends away from the normal