6.4 superposition Flashcards
state the principle of superposition
the principle of superposition states that when two or more waves of the same type meet at a point at the same time, the displacement of the resultant wave is the vector sum of the displacements of the individual waves at that point in time
how are stationary waves formed?
when two progressive waves of the same type with equal amplitude, equal frequency, equal speed travelling in opposite directions meet and undergo superposition with each other, a stationary wave is formed.
define diffraction
diffraction is the spreading of waves at an edge of an obstacle or through a slit so that the waves do not travel in straight lines
what is the single slit formula?
sin theta = lambda / b (b is slit width)
state Rayleigh’s criterion
for two objects to be just resolved, the central maximum of the diffraction pattern of one object must lie on the first minimum of the diffraction pattern of the second object
what is Rayleigh’s criterion formula?
lambda / b = s / r (s is the separation, r is distance from objects to slit)
define coherence and state when constructive and destructive interference occurs
two waves have a constant phase difference .
constructive: arrive in phase
destructive: arrive antiphase
what are the conditions for interference to be observable?
- waves must meet and be coherent
- waves must roughly be the same amplitude
- for transverse waves, either unpolarised or polarised in the same plane
- slit separation in the same order as wavelength
what is the double slit formula?
lambda = ax/d (where a = slit separation, x = half width of first maxima, d = distance from slit to screen)
what is diffraction grating formula?
dsintheta = n lambda where d = 1/number of lines per m, n = order of fringe starting from 0 in central bright fringe
