chapter 12 - waves 2 Flashcards
What two phenomena occur when a wave goes from a higher to a lower refractive index at an angle of incidence less than the critical angle?
The ray is refracted and partially reflected.
What is the principle of superposition
When two waves meet at a point the resultant displacement is the (vector) sum of the displacements of the individual waves.
What is constructive interference?
When two waves superpose in phase causing an increase amplitude.
What is destructive interference?
When two waves superpose in antiphase causing a decreased amplitude.
What are coherent sources of waves?
Sources that emit waves with a constant phase difference (and the same frequency).
What is an interference pattern?
A pattern of regions of constructive and destructive interference produced by coherent sources of waves.
What path difference is required for waves to be in phase?
A whole number of wavelengths
What path difference is required for waves to be in antiphase?
An odd number of half wavelengths
What is the relationship between path difference and phase difference for coherent sources?
(Path difference/wavelength) x 2π
What term describes a phase difference of zero between two waves?
In phase
What term describes a phase difference of π radians between two waves?
In antiphase
What is x in the double slit equation (λ = ax/D)?
Fringe separation
What is D in the double slit equation (λ = ax/D)?
Distance between the double slits and the screen
What is a in the double slit equation (λ = ax/D)?
Distance between the double slits
What occurs to cause a dark fringe in the double slit experiment?
Destructive interference of the light from each slit
What occurs to cause a bright fringe in the double slit experiment?
Constructive interference of the light from each slit
What did Young’s double slit experiment demonstrate about the nature of light?
That light exhibits wave behaviour.
What name is given to light of a single frequency/wavelength?
Monochromatic
Why did Young place a single slit before the double slit?
To ensure the light from each of the double slits was in phase.
What are the condition required for a stationary wave to form?
Two waves travelling/propagating in opposite directions superpose with the same frequency and similar amplitudes
What is an antinode on a stationary wave?
A point where the progressive waves are in phase and constructively interfering resulting in maximum amplitude
What is an node on a stationary wave?
A point where the progressive waves are in antiphase and are destructively interfering resulting in minimum amplitude
How many wavelengths are there between adjacent nodes of a standing wave?
Half a wavelength
What is the phase difference between points either side of a node?
Pi Rad/180 degrees
What is the phase difference of points between two adjacent nodes?
Zero
How does phase vary along a progressive wave?
Changes continuously across each wave cycle.
How does amplitude vary in a stationary wave?
It varies continuously along the wave. It is a maximum at antinodes and a minimum at nodes.
How does amplitude vary in a progressive wave?
It is the same at every point along the wave.
What type of wave doesn’t transfer energy?
Stationary waves
What is the fundamental frequency of a string?
The lowest frequency which produces a stationary wave on the string.
What factors determine the fundamental frequency on a string
Length, tension and the mass of the string.
What determines the pitch produced by a stationary wave in a musical instrument?
The frequency of the 1st harmonic
What determines the loudness of sound?
The amplitude of the sound wave
Why can only certain frequency stationary waves be produced on a stretched string?
There must be nodes at the fixed ends and only certain frequencies/wavelengths allow this.
What feature of a stationary wave is always formed at an open end of a tube?
(Displacement) Antinode
What feature of a stationary wave is always formed at a closed end of a tube?
(Displacement) Node
how do progressive waves differ from stationary waves?
progressive: all points have same amplitude, transfers energy
stationary: nodes and antinodes, does not transfer energy
