Chapter 11/12, Waves Flashcards
What is a progressive wave?
A wave transfers energy without giving a net displacement to the material through which it propagates.
What is a traverse wave?
In traverse waves like light the oscillations occur perpendicular to the direction of energy transfer.
What are the peaks and toughs of a wave?
The points of maximum displacement of a traverse wave.
What is a longitudinal wave?
A wave where oscillations are parallel to the direction of energy transfer. e.g. sound.
What is the displacement from a wave?
The displacement from the equilibrium position.
What is amplitude?
The maximum possible displacement.
What is the time period of a wave?
The total time taken for one oscillation.
What is wavelength?
The minimum distance between two points in phase in a wave, e.g. the distance between two peaks.
What is frequency?
The number of wavelengths passing a point per unit time.
What is the wave equation?
v=fλ (wave speed = frequency * wavelength).
What is phase difference?
The difference between the displacements of particles along a wave measured as an angle where π = λ/2.
State the law of reflection.
The angle of incidence is equal to the angle of reflection (angles measured from the normal).
What is refraction?
When a wave slows down or speeds up as it enters a material causing a change in direction.
What is diffraction?
When a wave spreads out as is passes a hole or goes round an obstacle.
When is diffraction most obvious?
When the size of the gap or obstacle is of similar size to the wavelength.
What is polarisation?
When the direction of oscillation is in only one plane.
Why can you not polarise a sound wave?
Because it is not a traverse wave.
Defining equation for intensity?
I = P/A (intensity = power / area).
What is the relationship between intensity and amplitude?
Intensity is proportional to amplitude^2 as velocity of oscillating particles is proportional to E^2 from the K.E. equation.
What is refractive index?
Defined as n=c/v (refractive index = c/speed of light in material) it is a constant for each material which shows how much it bends light.
What does the equation n sin(θ)=k show and how can it be used to find the angle of refraction between two materials?
Shows that refractive index*sin(angle in/out of material) is a constant, can be equated to itself for 2 materials to find the angle of refraction.
What is total internal reflection and what are the requirements for it?
Must travel from medium with high refractive index, the angle of incidence must be greater than the critical angle which is the point where the angle of refraction is 90 degrees.
What is the name given to the process of overlapping waves?
Superposition.
What is the net displacement given from the superposition of two waves?
The sums of the displacement of each wave (note displacement not distance, waves can cancel).
