constructive p.d (antinode) = nλ
'loud', 'light band'
or nλ = |S₁X-S₂X|
destructive p.d (node) = (n-0.5)λ
'quiet', 'dark band'
or (n-0.5)λ = |S₁X-S₂X|
one free end, one fixed (odd):
bigger Δx gives more refraction, more spread out
Δx=fringe spacing (m), λ=wavelength (m), L=distance from slits to screen (m), d=slit separation (m)
refraction & reflection:
where; n=speed of light in a vacuum/ speed of light medium
Young's double slit experiment
Young’s double slit experiment shows light exhibiting the wave properties of diffraction and interference.
Light can be polarised, observed as white light diffracts and colours are seen as a result. As only transverse waves can be polarised, the wave model of light is proven.
n₁=refractive index of first medium
θ₁=angle to the normal in first medium
n₂=refractive index of second medium
θ₂=angle to the normal in second medium
Transverse waves: particle moves along vertical axis
Longitudinal waves: particle moves along horizontal axis
Coherent waves: waves with the same frequency
Mechanical (sound, air, water) waves do not exist in a vacuum, they require a medium to travel through
Electromagnetic (light) waves can exist in a vacuum, do not require a medium
Travelling wave: a wave for which the crests and troughs travel in the direction of wave propagation.
Standing Waves: when 2 wave trains with the same amplitude and wavelength move through each other, the resulting interfering pattern results in a standing wave. Consists of alternating nodes and antinodes that remain in a fixed position, wave appears to be stationary/'standing'
fundamental frequency: n=1
formation of standing waves on a string:
1. waves reflect at both ends of string
2. reflections travel in opposite directions with the same frequency and amplitude
3. fixed ends are nodes, free ends are antinodes
Nodes & Antinodes
Constructive Interference: When waves in the same phase overlap, their amplitudes add together
Destructive Interference: When waves of different phases overlap, their amplitudes cancel
Nodes: Points of complete destructive interference
Antinodes: Points of complete constructive interference, largest amplitude
Waves reflect at the end of a string and are inverted if end is fixed
An object or system will resonate if driven at its natural frequency
Resonance greatly increases magnitude of oscillation in an object/system
Doppler effect is the detected frequency change due to the relative motion between a wave source and detector.
f increases when source and detector move towards each other
f decreases when source and detector move away from each other
independent: variable that is being changed (x-axis)
dependent: variable that is being measured (y-axis)