Chapter 5.2 - Wave phase and superposition Flashcards
What Is the cycle of one complete wave measured as
2Pie
What are wavefronts?
Lines connecting points on the wave that are at exactly the same phase position
What are wave fronts?
Lines connecting points on the wave that are at exactly the same phase position
What is constructive interference
The superposition effect of two waves that are in phase producing a larger amplitude resultant wave
What is destructive interference?
The superposition effect of two waves that are out of phase producing a smaller amplitude resultant wave
What is wave superposition
When waves meet each wave tries to cause a wave displacement at the point of intersection according to their phases at that location.
The net effect is that the overall displacement is the vector sum of the displacements caused by the individual waves.
What is a ray?
The ray indicates the direction of propagation of wave while the wavefront is the surface of constant phase
What are stationary/standing waves?
A wave that consists of oscillations in a fixed space with regions of significant oscillation and regions with zero oscillation which remain in the same locations at all times.
What does coherent mean In terms of waves?
Waves are called “coherent” if they have the same frequency and have a constant phase relationship
What is a progressive wave?
A means for transferring energy via oscillations
What are nodes?
Regions on a stationary wave where the amplitude of an oscillation is zero
What are antinodes
Regions on a stationary wave where the amplitude of oscillation is at its maximum
What is a sonometer
A piece of apparatus for experimenting with the frequency pf relationships of a string under tension, usually consisting of a horizontal wooden sounding box and a metal wire stretched along the top of the box
Why don’t stationary waves stick to the strict definition off a wave?
They don’t transfer any energy
String wave speed equation
v= square root of : Tension in string / mass per unit length
The fundamental frequency in a string equation
( 1 / 2xLength of string) X (SR of Tension in string / mass per unit length)
What is wave diffraction?
When a wave passes the edge of an obstacle the wave energy spreads into the space behind the obstacle.
What factors affect diffraction?
Size of the obstacle and the wavelength of the wave
Describe the diffraction pattern observed when light passes through a narrow slit
Central maxima, areas of darkness (destructive interference ((out of phase)), decreasing intensity.
What does the sum of displacement between 2 waves = if no light can be seen?
Total displacement = 0
What is the observations of narrowing the slit in a single slit diffraction?
Wider maximum, further maxima and minima
What is a diffraction grating?
A device that will cause multiple diffraction patterns which then overlap creating an interference pattern with a mathematically well-defined spacing between bright and dark spots
Equation for a diffraction grating?
wavelength x the order = diffraction spacing x sin (angle between original direction and the direction of a bright spot)
d must be in millimetres or metres for metres do 1/number per metre for millimetres do (1x10^-3)/number per mm
What is interference
The superposition outcome of a combination of waves. An interference pattern will only be observed under certain conditions such as coherent waves
What are the qualities of coherent waves
Same frequency
Constant phase relationship
What happens in the two slit experiment
Two waves are brought together to produce an interference pattern.
What is two-slit interference
Two-slit interference is a form of two-source intereference where the slits diffract existing waves to act as new sources of waves.
What is wave refraction?
Change in wave speed when the wave moves from one medium to another. There is a corresponding change in wave direction (Governed by snells law)
What is the refractive index of wave?
The measure of the amount of refraction caused by different materials
What is the refractive index equation
n can be defined in several ways but is fundamentally a result of change in wave speed…
refractive index = speed of light in vacuum/ speed of light In medium
What is snells law
n1 X sinx1 = n2 X sinx2
n=refractive index of material x= angle that the ray makes to the normal to the interface between the two media at the point the ray meets that interface
critical angle formula
sin x = n2/n1
Critical angle equation for light emerging into air
sin x = 1/n1
What is the critical angle
The largest angle of incidence that a ray in a more optically dense medium can have and still emerge into the less dense medium. Beyond this point the ray will be totally internally reflected
What is total internal reflection?
All wave energy is reflected inside the more dense medium.
Requirements for total internal reflection
The ray attempting to emerge from more dense medium
The angle between the ray and the normal to the interface is the greater than the critical angle
