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    EM Group velocity & phase velocity in dispersive medium

    Hello! My book here states that for a medium where the index of refraction n increases with increasing frequency (or wavenumber), "the group velocity is less than the phase velocity". This is stated for a wave which is the sum of two waves with equal amplitude and differing frequency...
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    In search for informations about commercial ceramic adhesives

    Is there a way to find detailed informations on chemical structure and mechanical properties of commercialy available materials? I am writing a thesis on ceramic adhesives: all literature I've found talks about "castable refractory adhesives" (because of ASTM classifications). However, it is...
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    Equivalent impedance

    hello I have a problem in calculating the equivalent impedance of a simple AC circuit, where the impedances are: Z1 = 5+i20 Z2 = 5+i20 Z3 = 10-i2,5 Z4 = -i10 Z5 = 5 and I need to find: Z_eq = Z3 // [(Z1 // Z4) + (Z2 // Z5)] where the + indicates 2 components in serie...