what is the difference between mechanical wave and electromagnetic wave?
mechanical waves require a material medium for propagation
electromagnetic waves can propagate without a material medium
what are transverse waves?
transverse waves are waves in which the oscillations of the wave particles are perpendicular to the direction of energy transmission
what are longitudinal waves?
longitudinal wave is a wave in which the oscillations of the wave particles are parallel to the direction of energy transmission
how does frequency, amplitude and velocity of a wave relate to that of a particle on the wave?
frequency of particle = frequency of wave
amplitude of particle = amplitude of wave
velocity of particle = v∘cosωt
velocity of wave = v = fλ
what is the shortcut for determining compression/rarefaction from dpslacement-distance graph?
both at x = 0 (equilm position)
compression is negative gradient
rarefaction is positive gradient
recall and use the term intensity
intensity is the rate of energy flow per unit cross-sectional area perpendicular to the direction of wave propagation
I = power/area = energy/area x time
energy = ½mx∘²ω² (from oscillations)
what is intensity proportional to?
I = kA²
what are the 2 cases for intensity?
1) 3D point source, area = 4πr²
since I = power/area, if power = const (no loss in energy), then I α 1/r²
hence A α 1/r
2) 2D point source, area = 2πr
recall Malus’ Law
I α I。cos²θ
what is the mnemonic to remember order of EM waves from lowest frequency, longest wavelength to highest frequency, shortest wavelength?
Ronald Mcdonald Is Very Ugly and eXtremely Gay
energy decreases
what is the wavelength of red light and violet light?
red = 400nm, violet = 400nm
what is the θ between 2 polarisers for all of the linearly polarised light to transmit through the 2nd polariser?
θ = 180° or 360°
what is the θ between 2 polarisers for none of the linearly polarised light to transmit through the 2nd polariser?
θ = 90° or 270°
