C3: Wave Phenomena Flashcards
What is a wavefront
A line or surface joining points of a wave that are in phase
What happens to a wave hitting a fixed end
The wave will be reflected with an inverted reflection
What happens to a wave hitting a free end
The wave will be reflected with an upright reflection
What are all the fractions in Snell’s Law
n1/n2 = sinθ2/sinθ1 = v2/v1
What is the critical angle
The angle of incidence in the optically denser medium for which the angle of refraction in the less dense medium is 90
What are the conditions for total internal reflection
A ray of light travels from an optically denser medium to a less dense medium
The angle of incidence in the optically denser medium is greater than the critical angle
What is diffraction
Phenomenon of bending or spreading of waves when they pass an obstacle, or pass through an aperture
What are the conditions to produce an observable interference pattern
The sources must be coherent (waves from each source have a constant phase difference)
The sources must have roughly the same amplitude
The sources must be either unpolarised or have the same plane of polarisation
How is the formula for fringe width used to obtain distance to nth bright and dark order fringe
Since the formula for fringe width is s = (λD)/d,
the distance x to the nth bright order fringe is
x = (n)(λD)/d
the distance x to the nth dark order fringe is
x = (n+0.5)(λD)/d
How does the width of the slit affect intensity distribution of a single slit
When a narrower slit is used, the central maximum becomes wider and the intensity decreases as less light gets through
When a wider slit is used, the central maximum becomes narrower and the intensity increases as more light gets through
What happens when the number of slits are increased in diffraction grating
Principal maxima has the same separation (the distance between each bright order fringe is the same)
Principal maxima becomes much sharper (width of maxima decreases)
Pattern increases in intensity as more light comes through the slits
Why does increasing the number of slits result in a narrower width of maxima
If there are more slits, interference from the rays coming from the many different slits at various angles do not give rise to constructive interference on the screen outside of the optimal angles that give the maximas.
