Chapter 12: Superposition Flashcards
Define a stationary wave
A wave where there is no propagation of energy and has nodes and and antinodes occuring at fixed positions
Define constructive interference
When two waves reinforce each other such that the resultant wave has a resultant amplitude of a maximum value
Define destructive interference
When two waves cancel each other such that the resultant wave has a resultant amplitude of a minimum value
State the 3 conditions for observable interference to occur
- Sources must be coherent
- The waves cannot be polarised in mutually perpendicular planes
- The amplitudes of both waves must be similar
State Young’s Double Slit formula
λ = ax / D, where
a = distance between slits
D = distance between screen and the slits
State the single slit diffraction equation
sinθ = λ / b, where
b = width of the slit
State the diffraction grating equation
dsinθ = nλ, where
d = separation between slits
Define diffraction
The spreading of waves when they pass through an opening or around an obstacle
State Rayleigh’s criterion
For 2 patterns to just be distinguishable, the central maxima of one must lie on the first minimum of the other. (θ = λ / b)
State the principle of superposition
When 2 or more waves meet at a point, the actual displacement is the vector sum of the separate displacements of the individual waves, and each wave proceeds as if no other waves exist
Explain why in a single slit diffraction, white light is observed at the centre but different colours are observed at the edges
White central region: All wavelengths of light overlap at the central maximum
Coloured edges: Different wavelengths of light diffract at different angles 0 so away from the centre, fringes will partially overlap; i.e. shorter wavelengths of violet light diffract less so are nearer the centre, while longer wavelengths of red light diffract more so are further away from the centre.
formation of stationary waves
