✔ 最佳答案
(c) Minimum inensity occurs when destructive interference occurs, i.e. the crest of T2 coincides with the trough of T1. Under such situation, the amplitude of the resultant wave = 3(Ao)/2 - Ao = Ao/2
Since intensity is proportional to the square of amplitude, hence the resultant minimum intensity is proportional to (Ao)^2/4
But it is given that wave with amplitude Ao has an intensity I, thus minimum internsity of resultant wave = I/4
(d) When the plane of oscillation of the wave aligns with the first polarizer, all wave intensity can pass through. The intensity component at 30 degrees with the first polarizer = I.cos(30)
Therefore, the amplitude of wave after passing through the second polarizer
is proportional to square-root[I.cos(30)]
Hence, amplitude = square-root[Ao^2.cos(30)] = (Ao).square-root[cos(30)]
The minimum aaplitude is clearly zero.
