3. Waves Flashcards
(34 cards)
What is a progressive wave?
A wave that transfers energy and not matter.
What is refraction?
When a wave changes direction when entering a different medium. If the medium is more dense, then it bends towards the normal, and vice versa.
What is diffraction?
When a wave spreads out due to its passing through a gap or around an object.
What is time period?
The time taken for one whole wave cycle.
What is frequency?
The number of wave cycles that pass one point in one second.
What is phase?
A measure of the position of a certain point along a wave cycle.
What is phase difference?
The amount that one wave lags behind another.
How are frequency and time period related?
f = 1 / T
What is the formula for wave speed?
C = fλ
What are transverse waves?
The displacement of the particles is at right angles to the direction of energy propagation.
Examples:
-Electromagnetic
-Ripples on water
-Waves on strings
-Some earthquake shock waves
What is a longitudinal wave?
When the displacement of particles is along the direction of energy propagation.
Examples:
-Sound waves
-Some types of earthquake shock waves
What is a polarised wave?
-A wave that only oscillates in one direction.
-It can only affect transverse waves.
-Achieved by passing a wave through a polarising filter.
-It can be used for glare reduction, and improving TV and radio signals.
What is the ‘superposition’ of waves, and what kind of interferences can it result in.
-Superposition is when one wave passes through another.
-Constructive interference is when the two waves combine to form a larger one, as they are oscillating in the same direction at that point.
-Destructive interference is when two. Waves combine and they are oscillating in different directions so their amplitudes cancel out.
-Total destructive interference is when two waves have the same amplitude (one positive and one negative) and so they completely cancel out.
What is a stationary/standing wave?
When two waves of the same frequency, amplitude and wavelength are travelling in opposite directions and they meet, so that no energy overall is transferred.
What is resonant frequency?
When a harmonic is formed because the frequency matches with the oscillating systems resonant frequency.
Where are the nodes and antinodes?
Nodes are where the amplitude is zero, ad antinodes are when the amplitude is at a maximum.
How dies diffraction differ depending on the size of the gap that it is passed through?
When the gap is:
-Bigger, there is no noticeable diffraction.
-Several wavelengths wide is when you get a noticeable diffraction.
-It diffracts the most when the gap is the same size as the wavelength.
-Smaller, most of the waves are reflected back.
How is diffraction most easily observed?
-With use of a laser, as it is monochromatic and coherent.
-When the gap is the same size as the wavelength.
How does the width of the central maximum differ?
-Increasing the slit decreases diffraction which makes it narrower.
-Increasing the wavelength increases the amount of diffraction so the intensity is lower.
What is coherence?
When two waves had the same wavelength, frequency, and have a fixed phase difference.
What are the formulae that describe when constructive and destructive interference happens in coherent waves?
Constructive: path difference = nλ
Destructive: path difference = ((2n+1)λ)/2 = (n + 1/2)λ
What is the formula used in Young’s double slit experiment that gives the fringe spacing?
w = λD / s
Where w is the fringe spacing, D is the distance between the screen and the slits, and s is the distance between the slits.
What is the diffraction grating equation?
d sin θ = nλ
Where d is the distance between slits, θ is the angle between the maxima and the normal, n is the order of the maximum and λ is the wavelength of the light.
What are absorption spectra?
A spectra where dark lines correspond with the wavelength of the light that has been absorbed.
