Statement I: In calculating the disturbance produced by a pair of superimposed incoherent wave trians, you can add their intensities.
Statement II: `I_(1) + I_(2) + 2 sqrt(I_(1) I_(2)) cos delta`. The average value of `cos delta = 0` for incoherent waves.

Options

A. Statement I is True, statement II is True, Statement II is a correct explanation for Statement I.
B. Statement I is Ture, Statement II is Ture, Statement II is NOT a correct explanation for Statement I.
C. Statement I is True, Statement II is False.
D. Statement I is False, Statement II is True.

Answer

a

Explanation

Average value of `cos delta` is
`(int_(t)^(t = T) cos (phi_(1) - phi_(2))dt)/(T) = 0`
Hence, `phi_(1)` and `phi_(2)` are constantly, randomly fluctuating phase of the two wave trains and integral is taken over a long time (relative to peridos of refractive waves.)