Waves Flashcards
Displacement
Distance from the equilibrium position in a particular direction
Amplitude
Maximum displacement from the equilibrium position
Wavelength
Minimum distance between two points in a phase on adjacent waves
Period of oscillation
Time taken for one complete oscillation
Frequency
Number of complete oscillations per second
Wave speed
Distance travelled by a wave per unit time
Transverse wave
A wave where the direction of oscillation is perpendicular to the direction of energy transfer
Longitudinal wave
A wave where the direction of oscillation is parallel to the direction of energy transfer
Example of a transverse wave
Light
Example of a longitudinal wave
Sound
Phase difference
Relates to the oscillation of two points on the (same) wave. How far ‘out of step’ one oscillation is from the other
Reflection
A change of direction of a wave at a boundary between two media, remaining in the original medium
Refraction
A change of direction of a wave due to a change of speed as it passes from one medium to another
Diffraction
When a wave passes through a gap or travels around an obstacle, they spread out
Polarisation
Particles oscillate along one direction only
Which type of waves can be polarised?
Transverse
Partial polarisation
More waves are oscillating in one direction only, but not all of them
Intensity of a progressive wave
Radiant power passing through a surface per unit area
Equation for intensity
I = P/A , I- intensity, P-radiant power, A- Xarea
Units of intensity
W/m^2
Intensity equation for a sphere
I=P/4πr^2
What is the relationship between intensity and amplitude?
intensity directly proportional to the square of the amplitude
List EM spectrum in order of increasing frequency
Radio, Micro, IR, Visible, UV, X, Gamma
Speed of light in vacuum
3x10^8 m/s
Refractive index equation
n=c/v
Snell’s law
n1sinθ1=n2sinθ2
Total internal reflection
When the light strikes the boundary at a large angle to the normal (angle greater than the critical angle), so it is internally reflected
Critical angle
Angle of incidence, which produced an angle of refraction =90
What are the conditions for coherent waves (4)
Same freq
CONSTANT phase difference
Same wavelength
Same amplitude
Interference
Combined effect of the disturbance cause by the each individual wave at the same place and time
Superposition
When two(or more) waves meet,
the (resultant) displacement is the (vector) sum of the
(individual) displacements add up
Progressive wave
A wave which transfers energy as a result of oscillations
Stationary wave
A wave which stores energy, where the shape does not move along
How does a stationary wave form on a string?
the wave reflected (at the fixed end of the wire) → interferes/superposes with the incident wave →
to produce a resultant wave with nodes and antinodes/no
energy transfer
Path difference
Difference in the distances waves have travelled
What is the need of a single slit in Young’s Double slit experiment?
To get the waves in phase, so the double slits act as 2 coherent sources
What equation is derived from Young’s Double slit exp?
λ=(ax)/D D- distance from the screen to the double slit, a distance between the fringes
Node
Node occurs where the amplitude/displacement is (always) zero
Antinode
Antinode occurs where the amplitude (of the standing wave) takes the only
maximum (possible) value
What is the distance between 2 adjacent (anti)nodes
half of a wavelength
Which particles are in phase AND out of phase AND by how much on a stationary wave
In phase between 2 adjacent nodes
Out of phase outside 2 adjacent nodes by π radians
What does fundamental frequency depend on?
String mass, tension, length
Fundamental frequency - f0
minimum frequency of a stationary wave of a string
What is always true for a standing wave in a closed pipe? (3)
Bottom is always a node
Top is always an antinode
F=(nv)/4L, L length of the pipe, v speed, n harmonic number
What is always true for a standing wave in an open pipe? (2)
- Each opening is always an antinode
2. The pipe must be nλ/2
