Chapter 11 - Waves 1 (pt1) Flashcards
Transverse wave examples
Waves on water surface
EM waves
Waves on a string
S-waves
Longitudinal wave examples
Sound waves
P-waves
Longitudinal wave diagrams
Show regularly spaced particles and then them moving left and right
Also show the direction of energy transfer
Show compressions and rarefactions
Axes on wave profile
y-axis is displacement
x-axis is time
Transverse wave
The oscillations are perpendicular to the direction of energy transfer
The wave represents the energy transfer so a particle at any point moves perpendicular to the wave in one direction
Longitudinal wave
A wave in which the oscillations are parallel to the energy transfer
How does a longitudinal wave work?
Particles vibrate and collide parallel to the wave
Results in areas with many particles (compressions) and areas with few (rarefactions)
Progressive wave
A wave in which the oscillations travel through a medium, transferring energy but not matter
Displacement
Symbol: s
Unit: m
Definition: The distance from the equilibrium position in a direction of a point on the wave
Amplitude
Symbol: A
Unit: m
Definition: Maximum displacement
Wavelength
Symbol: λ
Unit: m
Definition: Minimum distance between two adjacent points in phase
Period of oscillation
Symbol: T
Unit: s
Definition: The time taken for one oscillation
Frequency
Symbol: f
Unit: Hz
Definition: The number of wavelengths passing a point per unit time
Wave speed
Symbol: v / c (speed of light. (3x10^8 ms^-1)
Unit: ms^-1
Definition: The distance travelled per unit time
Already known equations
f = 1/T v = fλ
Phases of a wave
One full phase is 360° so 2π radians
The phase difference is the angle difference between points in waves of the same frequency at the same displacement
The fraction of the wavelength apart they are is the same as the fraction of 2π
Intensity
Power/Area
P/4πr^2 when given a distance, distance is r
The radiant power through a cross-sectional area
Intensity ∝
(Amplitude)^2
Oscilloscope
Gives you the wave in a visual way (trace) on a grid, the horizontal length of each time box is the time base
Frequency from an oscilloscope
- Read the peak-to-peak distance
- Multiply by the time base for the period
- Do 1/T for the frequency
Reflection
Wavelength and frequency stay the same
Draw a normal perpendicular to the surface, the angle between the incident ray and the normal is equal to the angle between the reflected ray and the normal
What do you draw on a reflection/refraction diagram
A normal
Refraction
Light refracts when it moves between mediums
If it enters a denser medium, it slows down, bending towards the normal
Constant frequency, wavelength changes
Draw to show some being reflected on a diagram
Diffraction
As waves pass through an aperture (gap) or pass around an obstacle, they will spread out (diffract)
The most diffraction happens if the width of the aperture is closer to the wavelength
What happens to water waves as they enter shallower water?
They slow down - shorter wavelength
Polarised waves
Transverse waves that only have oscillations in one plane - said to be “plane polarised”
Partial polarisation
When there are more waves oscillating in one plane but not exclusively
Happens to reflected waves
E.g. sunlight off a wet road
Where is a particle moving from a transverse ray diagram?
Perpendicular to the movement of the wave
