Waves Flashcards
Longitudinal vs Transverse waves
Longitudinal: Particles vibrate parallel to direction of energy transfer.
Transverse: Particles vibrate perpendicular to direction of energy transfer.
wavelength
difference between 2 successive identical points that have the same oscillation
Period
Time per oscillation
Frequency
Oscillations per unit time
Displacement
Distance a point is from its rest position
Amplitude
Max displacement
Wave equation
Wavespeed = Freq x Wavelength
Intensity Equation
I = Power / Area
Intensity & Amplitude Relationsjip
I is directly proportional to A^2
Diffraction
Spreading out of waves as it passes around an obstacle or through a gap
When is diffraction most pronounced?
When wavelength is similar size to the gap
Interference
The addition of 2 or more waves (superposition) creating a resultant wave
Order of EM waves (largest to shortest wavelength)
Properties of EM waves
Radio, Micro, Infra-red,Visible Light, Ultraviolet, X-ray, Gamma ray
Speed of 3 x 10^8
Have an electric & Magnetic wave interlocked at right angles to each other
What’s a plane polarised wave
What waves can be polarised?
Oscillations of the field & direction of travel are only in 1 field
Transverse
Malus’s Law
Amplitude after plane rotated
I = I_max cos^2(-). Max when (-) = 0. 0 when (-) = 90 A = Acos(-)
Refraction
How is speed + Direction affected when moving into a material of higher refractive index?
Refractive Index Equation
Wave changing speed & direction due to it passing from one medium to another
Speed decreases, bends towards normal
n = Speed of light in vacuum/Speed of light in material
Snell’s law
n1sin(-)1 = n2sin(-)2 OR nsin(-) = constant
Internal Refraction
Critical angle equation: in air, and between 2 materials that arent air
Result of both reflection & refraction when waves travel from high refractive index to low. Below critical angle: refraction & weak reflection. Equal to critical angle: Refracted wave travels along boundary. Above critical: All light is reflected.
SinC = 1/n SinC = n2/n1
Superposition
When 2 or more waves of the same type meet, the resultant wave can be found by adding the displacement.
Coherence
2 waves with a constant phase difference.
Phase difference & Path difference
Phase: Difference in phases of 2 waves of the same frequency.
Path: Difference in the distance travelled by 2 waves arriving at the same point.
Young Double Slit Equation
Conditions necessary
wavelength = fringe seperation x distance between 2 maxima / distance from slit to observed
wavelength = ax/D
Light must be monochromatic (same wavelength)
Must be an accurate method of producing and measuring a small path difference
Diffraction Grating Equation
n x wavelength = dsin(-) where n is order of maximum and d is slit seperation
Stationary waves
Waves formed by the interference of 2 waves travelling in opposite directions, with the same frequency & similar amplitude.
Node & Antinode
Node = 0 displacement Antinode = max displacement