11. Waves Flashcards
1
Q
Define a progressive wave
A
- An oscillation (vibration) that transfers energy but does not transfer matter
2
Q
Deinfe mechanical waves
A
- Progressive waves that need a medium to travel through
3
Q
Define electromagnetic waves
A
- Progressive waves that can travel through a vacuum
4
Q
Examples of mechanical waves
A
- Sound waves
- Tidal / water waves
- Seismic waves
5
Q
Examples of electromagnetic waves
A
- Radio waves
- Microwaves
- Infrared
- Ultralight
- Visible
- Xrays
- Gamma rays
6
Q
What are mechanical waves composed of?
A
Mechanical waves are composed of the movement of matter that transfer energy
7
Q
A
- As the progressive wave travels through the medium (material) the particles move from their equilibrium position
8
Q
Define transverse waves
A
- When energy is transported perpendicular to the direction of oscillation
9
Q
Define longitudinal waves
A
- When energy is transported parallel to the direction of oscillation
10
Q
Describe the characteristics of a wave diagram
A
- Compression IIIIIIII
- Oscillation <——–>
- Rarefaction I I I
- Energy ——->
11
Q
Name examples of longitudinal waves
A
- Sound waves
- P-waves in earthquakes
- Pressure waves
12
Q
Name examples of transverse waves
A
- EM waves
- Water waves
13
Q
Describe the similarities and differences between transverse and longitudinal waves
A
- Both transfer energy
- Transverse requires a medium, logotidom
14
Q
Define wavelength (lamda)
A
- The minimum distance between two points in a phase on adjacent waves
- Units are metres
15
Q
Define wave displacement (s)
A
- Distance from the equilibrium position in a particular direction; a vector, so it can have either a positive or negative value
16
Q
Define amplitude (A)
A
- Maximum displacement from its equilibrium position
17
Q
Define frequency (f)
A
- Number of waves passing a point per unit time
- Units are Hertz or per second
18
Q
Define time period (period of oscillation) (T)
A
- The time taken for a wave to move past a given point or the time taken for one oscillation
- Units are seconds
19
Q
Describe the relationship between frequency and time period
A
- They are inversely proportional
- f= 1/T
20
Q
State the equation for wave speed
A
- v = wave length x frequency
21
Q
A
Waves are oscillations therefore we describe the difference between waves with the use of angles in radians
π = 180 degrees
22
Q
Define in phase
A
- When a part of the wave continually has the same displacement
- The wave will have a phase difference of 0 or multiples of 2π radians
23
Q
Define anti phase
A
- When a part of the wave continually has the opposite displacement
- The wave will have a phase difference of π radians
24
Q
State the phase difference equation
A
- The phase difference
pitchfork = x/lamda x 360
25
Define a ray
* A representation of a wave
* A straight line with an arrow indication the direction of energy transport
26
Define reflection
* Occurs when a wave changes direction at a boundary between two materials
27
Define refraction
* Occurs when a wave changes direction and speed when passing from one material to another
28
* Reflection and refraction both occur when a wave changes direction at boundaries of different mediums
*
29
law and rules of reflection
* ø incidence = ø reflection
30
* When waves reflect their wavelength and frequency do not change
* A reflected wave gains an additional 90˚ phase difference from the incident wave
31
* Refraction is when the wave changes velocity (speed and direction)
* If the refracted ray bends towards the normal the wave has slowed down
* When the refracted ray bend away its speed has increased
32
1) Start with absolute uncertainty
2) Calculate uncertainties in quantities plotted
3) Uncertainty bars for x and y (vertical box plot)
33
Diffraction and direction
* When a wave passes through a gap they spread out, this is diffraction
* All waves can undergo diffraction
* The speed, wavelength and frequency of a wave does not change when diffraction occurs
* Diffraction only affects the waves direction
34
The magnitude of diffraction
* The amount of diffraction depends upon two quantities
* Wavelength of a wave
* Size of gap (or obstacle)
35
* Diffraction is increased when the size of the gap is comparable to the wavelength of the wave
36
* The relative size of a doorway and the wavelengths of light and sound is why you can hear someone around a doorway but you cannot see them
37
* Diffraction - only direction changes
* Refraction - refraction, velocity and frequency changes
38
* Wavelength of sound is compared to width of the door
39
Polarisation
* Waves are oscillations that transfer energy
* To date we have only considered waves that oscillate in one dimension
* Yet we live in a three dimensional world so it makes sense that the oscillations can be in three dimensions too
40
Define plane polarised waves
* Waves that oscillate in one plane (one dimension)
41
Define unpolarised waves
* Waves that oscillate in many possible planes
42
Is light from a filament lamp polarised or unpolarised?
* Unpolarised
43
Can longitudinal waves be plane polarised?
* The direction of energy transport is parallel to oscillation
* As their oscillations are limited to on plane it does not make sense to talk about them being plane polarised
* Therefore, we say longitudinal waves cannot be plane polarised
44
Reflected partial polarisation
* When transverse waves reflected off a surface they become partially polarised
* This means there are more waves oscillating on one particular plane but no completely plane polarised
45
* Unpolarised light - possible planes of oscillations
* Partial polarised light - Majority of oscillations in this plane
46
I = P/A
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