11 Progressive Waves Flashcards
Similarities between secondary and primary waves
Both are progressive waves
Differences between primary and secondary waves
Primary waves are longitudinal
Secondary waves are transverse
Progressive wave
An oscillation that travels through matter. They transfer energy but not matter
Displacement (wave)
Distance from the equilibrium position in a particular direction
Amplitude
Maximum displacement from the equilibrium position
Wavelength
The distance between two points on adjacent waves
Period of oscillation
The time taken for one oscillation to move one whole wavelength past a given point
Frequency
The number of wavelengths passing a given point per unit time
Wave speed
The distance travelled by the wave per unit time
v = f lambda
Wave speed = frequency x wavelength
f = 1/T
Frequency = 1/ period
In phase
Particles which oscillate perfectly in step with one another
Law of reflection
The angle of incidence is equal to the angle of reflection
Refraction
When a wave changes direction as it changes speed when it passes from one medium to another. This changes wavelength wave speed but not frequency
Meaning of FAST
Fast
Away
Slow
Towards
Diffraction
When a wave passes through a gap or travel around an obstacle they spread out. This does not changes speed frequency or wavelength
Polarisation
The particle oscillate along in one direction only. The wave is confined to a single plane. Longitudinal waves can not be polarised
Partial polarisation
When a transverse wave reflects off a surface
Intensity
The radiant power passing through a surface per unit area
I = P/A
Intensity = Power / Area (4 pi r^2)
What is the relationships between intensity and amplitude
Intensity is directly proportional to amplitude squared
What are electromagnetic waves
Magnetic fields oscillating at right angles to each other
Wavelength of radio waves
X>10^-1
Wavelength of microwaves
10^-1 >x> 10^-3
Wavelength of infrared
10^-3 >x> 7x10^-7
Wavelength of Visible light
7x10^-7 >x> 4x10^-7
Wavelength of ultraviolet light
4x10^-7 >x> 10^-8
Wavelength of x rays
10^-8 >x> 10^-13
Wavelength of Gamma rays
10^-10 >x> 10^-16
What is the speed of light in a vacuum
3x10^8
What is the order of electromagnetic wave
Radio waves
Microwaves
Infrared
Visible
Ultraviolet
X rays
Gamma rays
What is the benefit of polarising electromagnetic waves
Reduce interference
n = c/v
Refractive index = speed of light in a vacuum / speed of light through the material
n sin (theta) = k
Refractive index x sin (angle of incidence) = constant
Total internal reflection
When light strikes a boundary at a larger angle to the normal and the light is reflected back into the original medium
Conditions for TIR
Light must be travelling through a medium with a higher refractive index
The angle at which the light strikes the boundary must be above the critical angle
n sin(C) = sin(90)
Refractive index x sin(critical angle) = 1
