AS2 2.1 Waves Flashcards
What is the wavelength?
Distance between 2 successive crests or troughs/the distance a wave progresses in one period
What is the frequency in relation to waves?
Number of waves passing a point per second.
What is the time period in relation to waves?
The time taken for one wave to pass a point
What is a phase in relation to waves?
A phase specifies the location or timing of a point within a wave cycle
What is a wavefront?
A wavefront is a line joining points of the same phase in a wave. eg a crest
What is the amplitude of a wave?
The amplitude is the maximum displacement measured from the equilibrium point on a wave
What is a progressive wave?
A progressive wave is a wave that transports energy to the surrounding areas without transferring matter.
What do mechanical waves need to travel through?
Mechanical waves require a medium (water or air) to travel through, this means they can not travel in a vacuum (space)
Do electromagnetic waves require a medium to travel through?
No, they don’t. This means they can travel through a vacuum like space, and also at the speed of light.
What are two types of progressive waves?
- Transverse waves.
- Longitudinal waves
What is a transverse wave?
A transverse wave is a wave where the vibrations are perpendicular to the direction of wave travel
eg All electromagnetic spectrum waves (including light) , seismic s waves,
What is a longitudinal wave?
A longitudinal wave is a wave where the vibrations are parallel to the direction of wave of travel
eg Sound waves, seismic p waves, ultrasound
What are compressions and rarefactions?
They are areas of zero displacement
The Wave Equations
f = 1/T v = f x λ
f = frequency (Hz)
T = time period(s)
v = wavespeed (ms^-1)
λ = wavelength (m)
All waves in the electromagnetic spectrum in order of increasing frequency and decreasing wavelength
Type of wave Frequency Wavelength
Radio , 10^4 ,10^3
Microwave ,10^8 ,10^-2
Infrared ,10^12 ,10^-5
Visible Light ,10^15 ,0.5 x 10^-6
Ultra-violet ,10^16 ,10^-8
X-Ray ,10^18 ,10^-10
Gamma-Ray ,10^20 ,10^-12
Visible Light Spectrum Wave-lengths
(only need to know red and violet)
Violet = 380-450nm (400nm)
Indigo = 450-480nm
Blue = 480-510nm
Green = 510-575nm
Yellow = 575-585nm
Orange = 585-620nm
Red = 620-780nm (700nm)
What is a plane in relation to polarisation?
It’s a flat surface on which a straight line connecting 2 points would lie, examples of planes are the horizontal and vertical planes
What is unpolarised light?
Unpolarised light has vibrations (perpendicular to the direction of travel) in main planes
How can we polarise light?
Light can be polarised by passing the wave through a filter which limits the vibrations to one direction.
What is plane polarised light?
-Plane polarised light has vibrations in a single plane which includes the direction of wave propagation
-OR plane polarised light has vibrations in a single direction which is perpendicular to the direction of the wave propagation.
Polarisation by refraction
As rays are refracted, they are partially polarised in the plane which is perpendicular to the surface
Wave phase
One complete wave cycle is equivalent to 2pi radians or 360 degrees
In phase
Points on a progressive wave are in phase if the distance between them along the direction of propagation is equal to a whole number of wavelengths: 0, 1, 2 and so on
Anti Phase in relation to waves
If two waves are in antiphase then the distance between them along the direction of propagation is equal to an odd number of half wave lengths 1/2 lambda, 1 and 1/2 lambda and so on
