Quote:
Originally Posted by r.samanta  i think i have understood your problem. u are trying to solve the problem by phase difference instead of N(no of wavelengths)
in that case , look at my earlier solution , i think u have understood by now that you simply need to multiply the equation by 2 pi(remember 1 wavelength= 2 pi?)to get the corresponding phase difference. so phi(phase difference)=2 pi(2L glass n/lambda)- 2 pi(2L air/ lambda)
when you differentiate, L air is constant(no expansion for air as i told u earlier) so right part is zero.
finally 2 pi phase difference creates 1 fringe shift. after differentiating , divide by 2 pi -u get fringe shifts and will get the same answer. |
But why do I have to differentiate the phase difference? We said that for each 2Pi difference in phase, there is 1 fringe shift, so why are we differentiating the phase difference, which gives us the change in the phase difference / minute?