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Waves, Useful Equations, Polarisation, Stationary Waves, Diffraction,…
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Useful Equations
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f = (1/2L)x(√T/μ); This is for the First Harmonic, where T is tension of the string and μ(Mu) is the mass per unit length
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W = (λD)/s; W is width of fringe spacing, D is distance between slit and screen, and the distance between the 2 slits is s
dsin(ϴ) = nλ; ϴ is the angle between n=0 and n=1 (diffraction grating diagram) and n is the order of diffraction
Polarisation
By having 2 filters at 90 degrees in the direction of travel for a transverse wave, the wave can be polarised (effectively causing it to 'flat-line')
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Can be used for Sun Glasses, as the polarising lenses block some visible light from reaching your eyes
Can be used for transmission of Radio Waves, as based on the angle of the antennas it will pick up certain polaired waves (either Horizontal of Vertical)
Stationary Waves
Superposition is the principle that you add the two (for 2nd Harmonic) or more displacements of the wave together to get the final displacement.
In the event two waves are identical and they superimpose, the maximum amplitude will be much greater (double if 2nd Harmonic)/ they constructively interfere.
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Waves must be coherent in order to combine. This means that they've got the same phase difference, same wavelength and frequency, and a similar amplitude.
When two waves of opposite amplitude (half a wave cycle out of phase), they interfere destructively to equal 0.
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Diffraction
(For Monochromatic light and single slit) The results on a screen would appear to a (larger) bright central maxima, then a dark point of destructive interference, then thinner and dimmer bands of light where some Constructive Interference has taken place.
(For White light and single slit) In the very centre there would a bright white central maxima, followed by dark spots of destructive interference. Then, because different wavelengths of light are diffracted, creates a rainbow/spectrum of light (from shorter to longer wavlength (blue to red).
When there is a large number of slits, it is a diffraction grating. If a monochromatic laser was shon through, it could create a central maxima, followed by a large area of destructive interference, followed by a maxima. This can be used to measure wavelength, as the distance between the maximal 'will always be the same';
Progressive Wave
Transverse: Particles oscillate at a 90 degree angle to energy transfer (whole of EM Spectrum, waves on string, water ripples)
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Longitudinal: The particles oscillate in the same direction as the energy transfer - round a fixed point (Sound, Ultrasound)